that's the principle of bonus pp. it's not just 1% of each play - to be accurate it is:
416.6667 (1- 0.9994^Number_of_scores)
you know it from the wiki page linked above.
by number of scores it isn't meant that you get bonus pp for every play. you get bonus pp for every difficulty you have never played before.
if you go to "group by" and do it by "rank achieved" in your song selection menue, you can get an idea of how many number of scores you have if you count together all the numbers except for "no rank achieved". it is not perfectly accurate since only ranked maps count but that should give you an idea of which maps you play count towards the bonus pp system.
if you want to know your exact bonus pp
https://osu.ppy.sh/p/api this will help you.
now if you mean something that changes things beyond the bonus pp: i currently have 3675pp by my top 100 plays. i just added everything together. the program i mentioned above told me i have 380 bonus pp currently. 3675 + 380 = 4.055pp. but i have 4.070pp.
that is because it doesn't show the digits after the first digit in the top 100 plays even though they are there. instead of just 200pp a play could be ]199.5;200.5[pp, which you would also have to remember.