I use one monthly folder. My image counter was about 2300 (after a full loop... when will they use 5 digits?). When inserting my SD card to another Canon and back to mine, the image counter is now about 8000, in a new folder for the same month. Even after deleting the new images, folder, and .CFG file, my camera won't restore to the previous numbering.
What should I do?
I don't want to reformat my huge memory card. The issue in large number jump is the early recycling of image numbers, once copied to my computer. If one thematic folder happened to already host an older image with that number, this image will be destroyed and replaced, which is really bad. Plus, the incorrect ordering. (I already suffered a normal cycling once). I can't change the fact that Canon set none-unique (e.g. date based) or not-long (5-9 digits) numbers, so the only thing I can do is to have numbering progressing slowly. A jump of 5700 over 9900 is clearly not that way.