I know this is confusing but...
Currently, when you "stack up" inventory, the stacks form left to right, so if you have incomplete stacks, they're at the far right. Then if you do something involving these multiple stacks, like planting herbs, and don't use them all, you're left with 2 incomplete stacks again, requiring another "stack up." If the "stacking up" went right to left, the smallest stacks would be on the left and get used up first.