Coming from an Affiliate Manager stand point, it is very important that you ask each program involved how conversions compare.
There are many ways conversions are calculated, but remember each program will go for the figure which looks best.
1) Clickthroughs divided by number of accounts
2) Clickthroughs divided by number of real depositing accounts
3) Accounts divided by real depositing accounts
The list is endless but at the end of the day the best way to work out conversion is through number two, as this puts a real value on how much you spend to bring players through PPC and other paid mediems and gives you an EPC (estimated price per click) to work off.