Even as a native speaker from the US, the way Rory talks can be a struggle a few times. Don't feel bad about not getting it. Furthermore, yes converting everything to cm works just fine-- that is how I work. as Jeroen mentions, you have to make some decisions about rounding here and there. However, it is easy enough to work to +-1mm which is +-3/64". That is plenty accurate.

So after reviewing the videos I realized that the waist on the front panel is drafted exactly to the ``1/4 waist measurement`` in total, even with the seam allowance at the fly and side seam . That means the front panel as sewn up is actually 2*3/8" or 3/4" shorter than the measurement. That is why These two seam allowances are moved to the back piece. An additional question on Rory: is there a particular reason to moving both of these seam allowances to the back panel, other than shifting the side seam allowances even further forward? I could just as easily imagine accounting for the fly seam allowances on the front panel and transferring only the side seam allowance to the back.