Third guess for classic match play:
1) the number of your own strokes
2) holes played * 20 + the number of your own strokes
minus(!) the number of holes that weren't halved.
These two parts are shown and then - of course - added.
Proof 1 in two matches over 7 holes, one player won three holes for a 3 up, 25 strokes: 140 + 25 - 3 = 162 for part 2)
Proof 2 in a match over 11 holes, 40 strokes, one side won 2 holes, the other 3:
220 + 40 - 5 = 255 XPs in part 2)