How to reconcile Payouts and Reserve Amount

Hello,

I'm reconciling all sales that were invoiced and completed against the Payouts and Reserves. I have downloaded all reports to work out how Payouts and Reserve amounts are calculated but still doesn't tally. Downloadable reports does not match against payouts received. And if it did, there's a 'reserve amount' deduction.

Please can someone help how the Reserve Amount are calculated or what items does this consists of?

Thank you in advance.