Marble sized Follicles!

Hey guys, I finally figured out how to palpate and my female has 6 marble sized follicles. My question is how long until ovulation? How big do the follicles have to be for ovulation?

I think they say ovulation is usually somewhere around 40 to 45 millimeters. As a comparison, ping pong balls are 40mm.

thanks id say shes around 15mm