Imonggo sorts product stock numbers alphabetically and not numerically, since it allows users to use a mix of alphabets and digits for the stock number. Thru the alphabetical sorting, you might see stock numbers sorted as 1, 10, 11, 12, 13, 2, etc.
If you are using numerical stock numbers and want them nicely sorted consecutively, you may add leading zeros to your stock number. For example, 001, 002, 003 etc.