Yes, like Ventrue said, you don't use the numbers to line up the edges. You only use them to identify which edges correspond to one another. Then it's just a matter of aligning the tab to it's corresponding edge.
That depends on how you cut them out. Ideally, they should perfectly overlap, whether you can see both of them or not. So, for example, if you cut the piece without the tab so that exactly half the line remains, then it should overlap the other line by 50%.