bugs

I don't know if this is intended or not, but getting two or more of a multiple platinum achievement increases the platinum count, whereas multiples of gold/silver/bronze achievements don't increase their respective counts.

Eh, by multiple I meant repeatable.

Yeah, working as intended. From the August 22 release notes:

With the exception of the All Star trophy, repeatable platinum trophies now count multiple times towards your total platinum count.

Oh ok, so it's only supposed to apply to platinum achievements then?

Correct.