The UP55A program controller comes standard with 8 contact input (DI) terminals, but I only know 3 of the terminal numbers.What are the other 5 terminal numbers?

You can determine the other 5 DI terminal numbers from the model code.
-*2* means no. 301–306.
The others (except -*4*) are no. 501–506.
-*4* means 303–304, 309–310, and 503–504 are added.