It depends on the roller gap - the space between the blue rubber rollers.
On mine, I can get about 150 eggs on one shelf.
Caveat: The shelves were originally designed for Ostrich and Emu eggs so the gap was set quite wide at the factory - probably 2-3 inches. With chicken eggs you need a gap of about 3/4". This means you need more rollers than the factory shipped if you want to max it out with chicken eggs (and not end up with an omelet on the bottom of the Hatchrite).
You may need to cannibalize a shelf or two, to fill in the remaining shelves with rollers. I took a bunch of rollers removed from my second shelf and installed them in the top shelf. I use the shelf with all the rollers removed as a hatcher. Add some wooden dividers and some 1" x 1" galvanized cage wire to keep the newly hatched chicks and ducklings from hopping out.
So, If you have enough rollers you can do 150 eggs per shelf. If you are lucky, the person that owned the thing before you added enough rollers for a 3/4" gap. Otherwise it will take a bunch of wrench turning (and not much rocket science) to put things right. Check your roller belts when you are taking the rollers out. It is a lot easier to replace them all at once than it is to do them onesy-twozies when they break. Pretty much all of my belts were cracked/broken when I bought the thing a couple years ago.
Weight? Think small pickup truck. Mine is a two shelf model and it took 3+ people to get it up into my trailer. Also consider the size of the door opening in the room you plan on keeping one of these. I had about 1/4" clearance on my basement door. It was a royal pain getting it in there - I had to partially disassemble it to make it fit through the doorway. Its kind of a "ship in a bottle" affair now. :-)