Answer by taking a quote from the following article:

The 2012 phenomenon was a range of eschatological beliefs that cataclysmic or otherwise transformative events would occur on or around 21 December 2012. This date was regarded as the end-date of a 5,126-year-long cycle in the Mesoamerican Long Count calendar, and as such, festivities to commemorate the date took place on 21 December 2012 in the countries that were part of the Maya civilization (Mexico, Guatemala, Honduras, and El Salvador), with main events at Chichen Itza in Mexico, and Tikal in Guatemala. Various astronomical alignments and numerological formulae were proposed as pertaining to this date. A New Age interpretation held that the date marked the start of a period during which Earth and its inhabitants would undergo a positive physical or spiritual transformation, and that 21 December 2012 would mark the beginning of a new era.

The Tortuguero site, which lies in southernmost Tabasco, Mexico, dates from the 7th century AD and consists of a series of inscriptions mostly in honor of the contemporary ruler Bahlam Ajaw. One inscription, known as Tortuguero Monument 6, is the only inscription known to refer to b'ak'tun 13 in any detail. It has been partially defaced; Sven Gronemeyer and Barbara MacLeod have given this translation: Very little is known about the god B'olon Yokte'. According to an article by Mayanists Markus Eberl and Christian Prager in British Anthropological Reports, his name is composed of the elements "nine", 'OK-te' (the meaning of which is unknown), and "god". Confusion in classical period inscriptions suggests that the name was already ancient and unfamiliar to contemporary scribes. He also appears in inscriptions from Palenque, Usumacinta, and La Mar as a god of war, conflict, and the underworld. In one stele he is portrayed with a rope tied around his neck, and in another with an incense bag, together signifying a sacrifice to end a cycle of years. Based on observations of modern Maya rituals, Gronemeyer and MacLeod claim that the stela refers to a celebration in which a person portraying Bolon Yokte' K'uh was wrapped in ceremonial garments and paraded around the site. They note that the association of Bolon Yokte' K'uh with b'ak'tun 13 appears to be so important on this inscription that it supersedes more typical celebrations such as "erection of stelae, scattering of incense" and so forth. Furthermore, they assert that this event was indeed planned for 2012 and not the 7th century. Mayanist scholar Stephen Houston contests this view by arguing that future dates on Maya inscriptions were simply meant to draw parallels with contemporary events, and that the words on the stela describe a contemporary rather than a future scene.

what was the inscription?
Gronemeyer and MacLeod claim that the stela refers to a celebration in which a person portraying Bolon Yokte' K'uh was wrapped in ceremonial garments and paraded around the site.