This is typically due to currency conversions. When we (Geniuslink) do our conversion into USD, we apply the conversion rate from the day that commission was earned and use that. Partnerize uses the conversion rate at the time the report itself is run.
Each method has its pros and cons. With our system, the numbers remain consistent from day to day and month to month. With Partnerize's approach, the numbers more accurately reflect what you would be paid out if they were going to write you a check at that moment.
This discrepancy is usually fairly small, however, we have seen it fluctuate up to 3% at times, so be sure to view these reports with a skeptic's eye, as the actual amount at payout may be something different.
If you do see bigger that expected discrepancies please contact us so we can investigate your situation further.