Rough Opening issues for interior Pre-hung door

Do you know the additional height of your finished floor? If so add that to the 82¼". Most prehung doors have a large gap from the bottom of the door to the frame. This looks terrible when over a hardwood or tile floor. I usually cut the side jambs to close this gap and add 1/4" from this length for my RO.

Yes for 2", I'd cut the bottom of the door. If you have a hollow core door you may cut off the bottom spacer and have to glue it back in. Because you cut the bottom, you lowered your door and this door knob will be lower than the rest.

Added: I just reread your post and you are putting this over concrete. Hold your jambs off of the concrete by 1/2".

Don't forget the sub-floor or cleat thickness. Pre-hung doors are shorter than the jambs for ease of install when house is heated/cooled by forced-air, that gap acts as a return air path for that room. Otherwise it could help to un-balance the HVAC system. Building inspectors do check for this. Be safe, GBAR

you could put the doors in after the flooring is finished ( un less its carpeting ) your floor guys would appreciate that. Make sure to check the level over the threshold before you cut the jambs.