I think I might have figured out why the discrepancy.
If you go to this page for Agassi's records, it doesn't say "251" anywhere, but I added up all the wins in the ATP Masters Series table, and they add up to 251.
there's a note on the page underneath that table: Tournaments were designated as the 'Masters Series' only after the ATP took over the running of the men's tour in 1990.
So, Andre's wins at some of these tournaments from 1987-1989 (Indian Wells, Miami, Rome, Canada, Madrid) before they were designated "Masters Series" don't count as wins at Masters Series tournaments. I guess.
Yes, that's what I meant.
And yes, since Fed now has 252, it's moot.
Originally Posted by kingiskingfineon
yes but tied first
Well then he also has the record of ATP500 wins (tied with Sampras).