In your documentation you state that this plugin uses alphanumeric, but it seems to use natural sort order. That is that x7, x8 and x70, is sorted according to the number sequence of 7, 8, 70, and not ...

Natural sort is the process of sorting alphanumeric content as a human would sort. The normal alphanumeric sort will sort the following ['Test1','Hey1','Test2','Hey10','Test10','Hey2'] (unsorted) just ...