Measuring eyepiece NZ.6210-CM, 10x/22 mm SWF, micrometer, crosshair, (Nexius EVO)

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.