Uber "Miscellaneous Adjustment"

I've gotten $5-10 from Uber for "Misc Adj" before but I drove NYE and the payout just landed in my bank account, and they added nearly $100 extra for "Misc Adj". That's nearly an extra 20% on top of fares and tips.

I ain't complaining, but it sure has me wondering wtf it is and why Uber is giving out free money. How do they factor what it is and what it should be?