Legacy Lighting help please

I can't seem to get my tokens to emit light (to replicate Darkvision) out to 60 feet here's two tokens, top left is the player under my control and has vision, bottom right the monster token here are the settings I have input to give light, zero dimming and here , despite having 60 feet, the token can only see approx 40-45 feet away ... Advanced Fog reveals further ... but the light does not If I make the light emit to 75 feet... it just about works ... but 75 feet is not 60 feet Darkvision

A possibility... D&D 5E treats diagonals as being the same distance as a horizontal row or vertical column of squares.  This would make the "radius" of vision, be square.  Dynamic lighting works off of actual (circular) radius.  If your map is using the 5E measurement, that would be the difference in measurement between grid and vision.  Try on a map where you can measure the horizontal or vertical distance the token can see, and that will probably work out to be the distance you are expecting.

Roll20 very much prefers the optional rule for diagonals working as 5ft for first diagonal, 10ft for second diagonal. You can change this on each map by selecting the pathfinder/3E distance calculation instead of 5E.