Any tiny, unexplained set of numbers on their own line on the copyright page signify the reprints of this specific edition. For example, the third edition from 2001 may have been reprinted seven times. Then the numbers will look something like this:
10 9 8 7
(originally that line will have looked like this: 10 9 8 7 6 5 4 4 3 2 1, and then for each reprint one number was deleted from the right of that row)
or:
8 10 9 7
(originally: 2 4 6 8 10 9 7 5 3 1, deleted from both ends; this schema is used to keep the numbers centered on the page)
or any other schema this particular publisher uses.
The line of numbers was invented when reprints were made from film or printing plates, and instead of making a new film or plate for each reprint, the no longer correct number was scratched out. Old books, that were set in lead letters don't have this row because the relevant letters could more easily be exchanged. In old books (and in some books today), you will find something like this:
Seventh Printing, October 2016
(originally: First printing, January 2001)
Today, where printing is often direct from digital, some publishers no longer use this row of numbers and instead use a single number (e.g. Penguin Random House). Here you will see something like this:
7
(originally: 1)
If your numbers look significantly different, you'll have to provide a visual example of the whole copyright page.
The purpose of these numbers is for the publisher to know which print run a specific book belongs to, if they notice problems with it. The numbers are irrelevant for anyone outside the publishing house (except book collectors).
As a self-publisher, you don't usually need this row of numbers, as (a) you probably don't have a quality management in your publishing process and (b) your books will likely be print on demand, where there are no print runs and no reprinting.
