How to read it
A side conceding 0.8 goals per match with an xGA of 1.6 is living on goalkeeping and luck — regression usually follows. The reverse (conceding more than xGA) points to a keeper problem or finishing variance against them. The xG − xGA difference per match is one of the cleanest single numbers for true team strength.
Limits
Same caveats as xG: provider models differ, small samples mislead, and one match tells you almost nothing.