Wrong Holding Penalty Tooltip or Effect is wrong

[GAGA Extrem]

Your steward seems to compensate a good part of the penalty.
The remaining bonus could come from personal stewardship.

 

[Captain Gars]

You are supposed to get -75% from it. But notice that you have a +10% modifier also, which brings it down to -65%. The rest of the difference most likely comes from your Steward standing in the province to collect taxes which gives a large bonus as well.