Question: How long was the rule of the dynasty that was active when the Rosetta Stone was inscribed?

Context paragraphs:
Rosetta Stone (software): Rosetta Stone Language Learning is proprietary computer-assisted language learning (CALL) software published by Rosetta Stone Inc.  The software uses images, text, and sound to teach words and grammar by spaced repetition, without translation.  Rosetta Stone calls its approach Dynamic Immersion (a term which has been trademarked).

Ptolemaic dynasty: The Ptolemaic dynasty (Ancient Greek: Πτολεμαῖοι , "Ptolemaioi"), sometimes also known as the Lagids or Lagidae (Ancient Greek: Λαγίδαι , "Lagidai", after Lagus, Ptolemy I's father), was a Macedonian Greek royal family, which ruled the Ptolemaic Kingdom in Egypt during the Hellenistic period.  Their rule lasted for 275 years, from 305 to 30 BC.  They were the last dynasty of ancient Egypt.

Rosetta Pebble: Rosetta Pebble is an American rock band from Detroit, Michigan.  Their name is a vague reference to the ancient Rosetta Stone.  Rosetta Pebble achieved a small degree of popularity in Detroit, parts of Michigan, and northern Indiana during the first half of the 2000s due to the band's folky, pop songs.  Influenced by folk rock (most notably the music of Cat Stevens, James Taylor, Jack Johnson, the Beatles and Pete Townshend), Rosetta Pebble play a more pop-oriented variation of folk rock.  The band is also commonly classified into the category of acoustic/soft rock.

Great Mendes Stela: The Great Mendes Stela is a commemorative stele erected during the Ptolemaic dynasty by Ptolemy II Philadelphus for Mendes, Lower Egypt.  Ptolemies III through V also had stelae: the bilingual, three-script Decree of Canopus and the Rosetta Stone.

Gubyaukgyi Temple (Myinkaba): The Gubyaukgyi (alt.  Kubyauk-gyi) temple, located just south of Bagan, Myanmar, in Myinkaba Village, is a Buddhist temple built in 1113 AD by Prince Yazakumar, shortly after the death of his father, King Kyansittha of the Pagan Dynasty.  The temple is notable for two reasons.  First, it contains a large array of well-preserved frescoes on its interior walls, the oldest original paintings to be found in Bagan.  All of the frescoes are accompanied by ink captions written in Old Mon, providing one of the earliest examples of the language's use in Myanmar.  Second, the temple is located just to the west of the Myazedi pagoda, at which was found two stone pillars with inscriptions written in four, ancient Southeast Asian languages: Pali, Old Mon, Old Burmese, and Pyu.  The inscription on the pillar displayed by the Myazedi pagoda has been called the Burmese Rosetta Stone, given its significance both historically and linguistically, as a key to cracking the Pyu language.

Fort Julien: Fort Julien (or, in some sources, Fort Jullien), also known as the Fort of Qaitbey (Arabic: قلعة قايتباي) is a fort located on the left or west bank of the Nile about 5 km north-west of Rashid (Rosetta) on the north coast of Egypt.  It was originally built by the Ottoman Empire and occupied by the French during Napoleon Bonaparte's campaign in Egypt and Syria between 1798 and 1801.  The fort became famous as the place where the Rosetta Stone was found in 1799.

Rosetta (software): Rosetta was a dynamic binary translator for Mac OS X that allowed many PowerPC applications to run on certain Intel-based Macintosh computers without modification.  Apple released Rosetta in 2006 when it changed the instruction set architecture of the Macintosh platform from the PowerPC to the Intel processor.  The name "Rosetta" is a reference to the Rosetta Stone, the discovery that made it possible to comprehend and translate Egyptian hieroglyphs.

Porl King: Porl King, born 19 October 1967 on the Wirral Peninsula in England, first achieved public acclaim and success as the singer, songwriter and guitarist for the goth band Rosetta Stone from their inception in the late 1980s through to their demise in 1998.  Since disbanding Rosetta Stone in 1998, he has pursued a career in digital audio and Pro Tools production.

Rosetta Project: The Rosetta Project is a global collaboration of language specialists and native speakers working to develop a contemporary version of the historic Rosetta Stone to last from 2000 to 12,000 AD; it is run by the Long Now Foundation.  Its goal is a meaningful survey and near permanent archive of 1,500 languages.  Some of these languages have fewer than one thousand speakers left.  Others are considered to be dying out because government centralization and globalization are increasing the prevalence of English and other major languages.  The intention is to create a unique platform for comparative linguistic research and education, as well as a functional linguistic tool that might help in the recovery or revitalisation of lost languages in the future.

Rosetta Stone: The Rosetta Stone is a granodiorite stele, found in 1799, inscribed with three versions of a decree issued at Memphis, Egypt in 196 BC during the Ptolemaic dynasty on behalf of King Ptolemy V.  The top and middle texts are in Ancient Egyptian using hieroglyphic script and Demotic script, respectively, while the bottom is in Ancient Greek.  As the decree has only minor differences between the three versions, the Rosetta Stone proved to be the key to deciphering Egyptian hieroglyphs.

Supporting paragraphs: Rosetta Stone Ptolemaic dynasty
Answer: 275 years