1001AP from 660ap? Free Bonus AP bug

I just had a match in which a player claimed to have 1k AP.

I wouldn't have paid it any attention if this was a Veigar, but it was a Katarina player.

Thing is, she did actually have 1001 AP!

Not only that, her build only provided a total of 510 AP before amplification.

Checking runes and masteries, and even being generous with rounding, at level 18 she gets 110 ap (actually 105.16) which could bring her to a total of about 620. Adding in , 660 ap before amplification.

Now, there's 30% amp from Rabadons and 5% from Masteries. Let's just assume they stack multiplicatively so the total is as high as it can get.

660 ap becomes 900 AP.

By calculation, that's still 100 ap short.

WHERE DID THIS AP COME FROM?? Are all AP champs getting some miscalculated boost in AP? Is it just Kat?

Every advantage is an advantage. This needs to be looked at. @Riot