ECBonus:
Best of Par 3 or 5 scores do not affect your avg. when played
With what ECB said in mind...
Don't worry about how far under par you shoot as much as just total score....
Since our averages are based on 18 hole scores and 9 hole scores are doubled to count as an 18 hole score a 30 for 9 holes will double to 60, 31 doubled to 61 etc, etc.
If you pay attention to much to, let's say a -4 for 9 holes, then that could mean a 30 for one 9 hole track, or it could mean a 32 for another. That "-4" could turn out to be a 60, 62 or 64 that's used in your average.