For transparency on how your final pp is calculated, pp gained from the beatmap is given along with weight (% of eligible pp to be gained for final pp). Only your highest pp score's beatmap gives you full pp. Other scores' pp values will be multiplied with decreasing percentage. The percentage is always rounded to the next whole number for displaying, but for calculations it is not. For example a score can be weighted by 0.48% despite the display saying "0%". If n is the amount of scores giving more pp than a given score, then the score's weight is 0.95^n .
It follows, that your total pp is computed as follows. Let PP contain each score's pp value. PP[i] denotes the ith score's pp value, sorted decreasingly, where i goes from 1 to n, and n is the amount of scores you have.
Total pp = PP[1] * 0.95^0 + PP[2] * 0.95^1 + PP[3] * 0.95^2 + ... + PP[n] * 0.95^(n-1)