What course? Was it 9 holes or 18 holes?
Minus 2 after playing 18 holes on a par 72 track is a score of 70. Minus 2 on a par 70 course after 18 holes is a score of 68.
What counts towards your stroke average is the total number of strokes, not how many under or over par you are at the end of your round.
Minus 2 after 9 holes on a par 72 track is equivalent to, and used for your stroke average, as an 18 hole score of -4, or 68 strokes.
Minus 2 after 9 holes on a par 70 track is equivalent to, and used for your stroke average, as an 18 hole score of -4, or 66 strokes