There are bugs...the most prominent and likely easiest to fix is one where you need to erase number(s) and redo a cell or more. Rather than it going back to next avl number, it continues numbering as if you never erased.
For example, when I get to number 11, I realize 7, 8, 9 are in wrong cells. I erase 7,8,9 and therefore next number I fill should be 7...instead the next number is 11 or 12 (depends on whether 11 is static or not. Clicking another few cells sometimes fixes, but there is a flaw in "next number" once you erase. I uninstalled for now as it is annoying. Will try again after bug fixes.