Resolution is defined in Lowrance Mercator Meters per Pixel (MM/pixel). A Lowrance Mercator Meter is roughly equal to 1 meter at the equator.
Simply put, the native resolution is displayed from .75x to 1.5x of the resolution. For example, a 4 MM/pixel image is displayed from 3 MM/pixel to 6 MM/pixel.
A Min of 1 and Max of 16 is creating layers at 1, 2, 4, 8 and 16 MM/pixel.