Hi India,
A level above about 15 indicates that ovulation has occured though usually we want to see a level in excess of 20. If you are on clomid usually we want to see the levels around or above 40. (this will depend on your practitioners preference)
I will copy and paste a chart here and these are the Australian values. You will see the variation of normal is quite vast.
Just keep in mind that you need to count 7 days from ovulation before you do the test. Progesterone levels should peak 7 days before your next period.

Male adult: < 2 nmol/L
Female:
Follicular phase: < 2 nmol/L
Luteal phase: 5 - 90 nmol/L
Post-menopausal: < 2 nmol/L
Pregnancy:
1st trimester: 30 - 150 nmol/L.
2nd trimester: 50 - 460 nmol/L
3rd trimester: 170 - 800 nmol/L

I hope this helps. Good luck on your journey...