Progesterone levels on clomid.. I need this explained.

Tessa
I did 50 mg of Clomid last month. My day 21 levels were less than 1. I should have asked her to explain what the levels meant in more detail because I don't understand. I see people on here saying 5 is normal some saying they should be over 15. Can someone try to help me understand progesterone levels and how it all works with clomid?