A question similar to this was recently asked about Clickbank
Can anyone give a clear definition of gravity re: Clickbank
Neither Clickbank or Paydotcom has the type of programs I prefer to promote but I can tell you some of the basic things.
With Paydotcom the APS is Affiliate Power Score. Paydotcom keeps a few things about it secret to try to keep people from abusing it.
The score is computed daily basis with the number of sales, total refunds, and affiliate earnings being a big portion of what is taken into consideration. They put importance on the number of unique affiliates making sales during the last 150 days. They give more importance to the most recent sales.
There is more to it but I've covered the most important points.
Also, I assume you are possibly asking about data entry programs. I won't talk about any particular data entry program. But if you are interested in something in general about data entry programs, here is a thread that could be helpful
Data Entry?