Strange sorting

I thought that when sorting on multiple columns the second sorting would come into play when the first colomn is the same. But look at this picture: I have sorted first on the left column and then sorted ascending on the second. But why is this column not sorting correctly?
1 answers

I am unable to find the error in this screenshot. The first column has 2 unique items (*10004 and *30004) and the second column has two corresponding blocks which are each sorted as well.