When you see a user's "number of write-ups", this is a number which PerlMonks maintains, incrementing it each time a user posts. Maintaining this number statically is more efficient than re-counting the user's writeups each time someone wants to see it. However, over time this number can "drift" away from the true count, due to a few rare conditions (let's not call them bugs). This is why "~" appears before the write-up number on Perl Monks User Search (it stands for "approximately").
For another reason why a user's displayed "number of write-ups" may not match their true count, see Why are categorized questions and answers displayed separately from the rest of my writeups?. Or, if you are a member of pmdev looking at a fellow pmdevil's writeups, then you may also see non-public nodes (such as patches) listed which are not accounted for in their "number".
If you suspect that the number of your write-ups displayed is inaccurate, you can reset it by doing the following:
There is no way to correct another user's write-up number. You could try /msging them and pointing them to the procedure above.