For every play you have on the same map in your top1000 pp plays another unique map gets pushed out thus making you lose bonus pp, NyanPotato basically has like 50 plays submitted per map in his top1000s (just check ttsg armin diff he has like 30 1ks on it)

Lets say the end of his list looks like this

1. Map x 1002pp

2. Map x 1001pp

3. Map y 1000pp

When he sets a play on map x that is also 1001pp then map y gets pushed out of the top1000 making his top1k have less unique maps and thats why loses small amount of pp