Is 11.5 progesterone ok?

Pregnant and Tired
I have some light spotting today at 6 weeks 4 days, mostly brown. My progesterone level is 11.5 (normal is 9-29, so on the low side) and the HCG was over 10,000 (normal 1060? to 39,000), so that was pretty good. I'm worried about the progesterone since it is on the bottom side of normal. Does anyone know if 11.5 for progesterone at 6 weeks 4 days is anything to worry about? I am waiting on a call back from the doctor. They did an ultrasound today and the heartbeat was 121 and the baby was measuring to the day the right size. Thoughts?