yadcf order number in dropdown menu

Dear all,

I have a dropdown menu in yadcf filter with some numbers. I'd like that the numbers to be sorted from the smallest to the largset (1, 2, 3, 4, 5, 6 etc). But now the number 10,11,12 are before than number 2 (1,10, 11, 12, 2, 3 etc). Is there a way to order appropriately?

Thanks and regards, Marco B