What's the trick?

I've had similar problems in other digital systems. What do you do to get a Phase back to number your images starting where YOU want it to? The manual doesn't say. I had to switch backs because of a problem with the one I purchased, and I put a card with which I had been shooting with back #1 into back $2 (both are P45+ backs). Back #2 is giving me frame numbers based on its history and ignoring the numbers already on the frames on the card. As a result, I will soon have duplicate file names, as the numbers from back #2 catch up with back #2. I manually changed the last shot files numbers to numbers in a safe range, but the back ignored this, and continued its numbering scheme.

What's the trick?