Does a gravid female lay inverted before ovulation, after ovulation, or can it happen anytime during their pregnancy?

This is my first attempt at breeding BP's, and I have been following Markus Jayne's EXCELLENT tutorial (http://www.ballpython.ca/gallery/breeding.html), but I wasn't too clear about the laying inverted part. She just shed on June 15th...and I was thinking that it was her pre-lay shed, but I could be wrong since I am not 100% sure that I saw her ovulate.

Thanks guys and gals....
-Lou