The range limiter on the 70-300mm G SSM has 3 positions, (Full AF), (Infinity-3M) and (MF). The first and last are self explanatory, the middle one is as I said above and limits the focus travel from Infinity down to 9 Metres. Some other lenses I have with focus limiters have a low and a high setting, which works differently. The 70-300 has an SSM motor and it doesn't go to infinity and back to get a reference point like non SSM lenses. I think.
Cameras, Sony A700, A850, A77, Lenses, Sony 70-300G, 16-80CZ, 28-75 f2.8 SAM, Minolta 500 f8 Reflex, 300 f4 G, 200 f2.8 G, 100 f2.8 (D) Macro, 50 f1.7, 28 f2.0, 28-135 f4, 70-210 f4, Sigma 21-35 f3.5-4.2. Minolta TCs x1.4 & x2.