I have a lighting rep that is telling me he has a 4' 2 lamp t8 surface mount fixture(4100 series lamps) that will produce the same amount of light as an existing 4' 4 lamp t12 34W cool white fixture. I don't see where he's getting the extra lumens from with just 2 tubes. Any thoughts? I'm finding the t8 lamps produce about 2800 lumens, not sure what the old t12's give out.