I don't mean to butt in. I have been using an ultrasound for 4-5 years and tipicaly what I have seen is.

8-10mm folicals are just sitting not doing much.
15 mm folicals have about 90 more days to ovulation
20 mm folicals have about 40 more days
30 mm folicals have 20 days left
and they ovulate when they are between 45 and 50mm

Now I also had a female sit at 35 for 2-3 months. She reabsorbed since the male was a dud.