When the Second Edition comes out, it suggests there have been two revisions to the copy. Accordingly, you can have a First Edition with many printings. It is not a true First Edition with all the numbers from 10 to 1. The numbers can be any amount. It is dependent upon how many printings the publisher anticipates.
Some books can carry an alphabetic series along with or instead of the numeric one.
A letter is deleted with each successive printing. This practice dates from around the Second World War. Entries in books published before that time show even greater inconsistencies and provide and even greater challenge to the collector. .