I'm going to try and use my Bencini Koroll II today. I've loaded it with film and don't really know how to advance it. The numbers on a 120 roll are for 6x4.5, 6x6, and 6x9. This Koroll is 3x4.5, and there is two advance windows. Which do I use because only the 6x6 numbers are visible? Any suggestions? That is the 1 in the right window.