how is lot number auto - generated?

Summary:

What is the logic behind auto generation of lot numbers?

Content (please ensure you mask any confidential information):

We kept the total length of 5, with a prefix of B (B0000-B9999).After some round of testing in SIT, we started getting the error of total length limit reached. We even tried to change the prefix to C, but still the same error was coming. Does it mean that no matter the prefix, the system will only take the numerical values while generating the lot?

Also, We checked in the backend, next value value is 50026:

Query - select INV_LOT_NUMBERS_S.nextval from dual