setSelection method logic

Hi guys.

Could you explain me the logic of the setSelection methods for my case?

E.g. I have a pattern `(111) 111-1111`. I want to edit number starting from the fourth digit.

So, I call `setSelection({start: 6, end: 6})`, but... Oh! That sets selection to `{start: 4, end: 4}`! Ok, I think, it's okay if it works correctly. But.. when I try to paste some digits it just skips first of them and only after this skipping selection becomes `{start: 6, end: 6}`. Of course, other numbers paste normally after that.

So, tell me pls what's the logic of this work and if there are mistakes how should it work?