If you remember how many you used, you can skip some and
continue to use...
For example, if you use 15 times on the films, and reload the film for some reason...
You load the film first, and than use lens cover on your les
than , set your camera be 1/1000 or 1/2000 shutter, F16 or smaller..
than, just tak 16-17 times on your camera ( of course do not remove the lens cover !)
than you can go back to use your film and skip the first 15-16 pcs.....
thanks