After update-what can I delete from old versions?

Hello.
I used the tip from Juggledad when updating from 3.4.9 to 3.5.1 (see below). And then I did the same to 3.5.3

So I have a lot of folders with old atahualpa-versions in them now

My question is: Which of the old ones do I dare to delete without getting problems? Can I delete 3.5.1 or do I need that?

(Update: what I actually just did was I installed 3.5.3 on my server and then activated that version instead of the old, and all settings from the old in some magical way was merged in to the new version)