I assume that you live in a new condo apartment building? I also assume that you own the parking space(s)? If so, something does not quite sound right. It is possible that the apartment would be assessed separately from the parking space, but they should both be assessed at the residential (not multi-residential) rate. I am baffled as to why the garage area would have a commercial assessment, unless part of it is being rented on a commercial basis.
You are no doubt aware that both the multi-residential rate and the commercial rate are higher than the residential rate.
Ask your property manager. If they can't give a satisfactory answer, I would think that an enquiry to the Municipal Property Assessment Corp. would be in order.