It seems to me that
- the site you are linking FROM must have at least 200
- the rep in the site you are linking TO will be boosted by 100 (not the one you are linking FROM) (I could be wrong here, I don't know what happens if the one you are linking to already has 200+ rep)
- it should be OR not AND. The current wording sort of implies that you need to link to all 4 to get 100 bonus rep points.
I suggest this wording instead:
- Linking accounts between Stack Overflow, Server Fault, Super User and meta from any account with at least 200 reputation: +100 reputation on each site linked to
This reflects my recent experience, at least. Whether it is the desired behaviour is up to people other than me :-)