10-12 stikeouts for a pitcher in a single game is indicative of how well he pitched.
10 K's indicates the following:
- at least 4 innings pitched but likely 6-8 innings
- 10 out's were recorded by the pitcher
- 10 times the opposing hitters failed to reach base
- Those K's are also indicative of how effective that pitcher was. 10K's 6-8 IP will likely reveal a low opponent score.
3K's for a batter indicates 3 outs. It doesn't indicate a single thing about how he did other than he made three outs.