Simplify the following text for a Grade 5 native English-speaking person.
Original: An extended ZIP +4 code , introduced in the 1980s , includes the five digits of the ZIP code , a hyphen , and four more digits that determine a more precise location than the ZIP code alone .
Simplified: The basic ZIP code is made up of five numbers . An extended ZIP + 4 code includes the five digits of the ZIP code , a hyphen and then four more digits .