IGM pay question

[threeonefour]

you know how it asks for a check # associated with your checking account.

i am all out of checks, and therefore out of numbers. i'd like to make a deposit soon to take advantage of the party reload. lets say i have written checks for the numbers 1000-1500.

could i just make up a number? like 1600? i have never had a 1600 check printed so there is no reason for the bank to think a 1600 check would be valid.

am i in the clear if i just doesn't use a number already used?