rough opening - prehung door

I'm trying to install a 32"x80" prehung door from home depot. The packaging on the door says my r.o. should be 34 1/2" by 82". My framing is correct, but when I put the door in the hole there seems to be an awful lot of gap to shim - approximately 3/4" on both sides and 1/2" on top! Maybe I don't understand the rough opening. Is it supposed to be "padded-out" with plywood,drywall,etc. after framing and before the door is hung?

 

34 1/2" is a little wide for my taste. I'd put a strip of 1/2" OSB on one side to shim it down to 34". That ought to make it easier to shim.

I like to shim the hinge side before I put the door in. Nail pairs of shims onto the rough opening right behind where each of the door hinges will be, using a 6' level to ensure you have them plumb. (Always use shims in pairs, facing opposite directions so that you can slide them to change the amount being shimmed) If you plumb the shims, then when you put the door in, the first thing you can do is nail the hinge side, then work the top and latch side.