Yes, a little confusing, but think of how the roll is when you open the wrapper. Yes, it is wound rather tight isn't it? That means the film emulsion is tight up against the number printed on the backing paper from the frame or several frames before it. That means it the ink used for numbers is might chemically release some sort of harmful vapor to the emulsion or if the ink/paint is still damp it might leave it's imprint on the emulsion. If you have a negative with the edge frame number of 10 and the shadow number is 10 then I'd say it's a red window problem. If it is frame 10 and you have some other number then I'd say you have a transfer problem. Mine with Efke was a window problem, but like Simon Says don't leave the window uncovered for any length of time of in very bright light, use tape. I left my camera unused and exposed to light many days before I finished the roll. On some frames there was nothing since I advanced the film for several shots rather quickly and light didn't have time to penetrate the backing paper. I always use tape now since one of the shots on the Efke was of a very good friend who has since passed on and just above his head, in the sky, is the number 6 or 9 whichever way you want to look at it. Lesson learned, as usual, the hard way. JohnW