Typical MTB race would be a 10K course for beginners, 20K for sport riders, and 30k for expert riders. Course time will depend upon the terrain and the weather.

One way to determine how "good" your results are is to compare your time and distance to the winning expert class time and distance - how far off, after adjusting for the time/distance ratio, was your time per lap... a far mor reasonable approach - especially for your ego - would be to do these same comparisons for the sport class winners. If your ratios are up these with the Expert class times, then work on your distance and move up a class.