Objective PL S-Apo, BF, LD, flat, S-Apo, AL/DL 100x/, w.d. 0.5mm,

This refers to the magnification factor of a single microscope lens. A lens with the number 40 is referred to as a scale of 1:40 or simply a factor of 40 times. If you multiply the lens factor by the eyepiece factor, you get the magnification.