What catalog are you using? In the United States the most common catalog it the Scott catalog.
Example line:
62 A6 1sh orange & blk 2.10 3.25
62 is the number
2.10 is the unused evaluation
3.25 is the used evaluation
It is worth 3.25 if it is in excellent condition and used in the proper time period. Otherwise someone could take unused 2.10 stamp and make it worth 3.25 by using it.
For more information see:
https://www.scottonline.com/ScottCa...Tutorial.pdf