I am tying to use the custom grid as a scale bar but it I can't seem to make it match the ruler or the guideline preset. These show correctly yet the custom grid, even though set to 0.001 gridlines per millimetre (which I would expect to draw 10cm squares to scale) doesn't seem to match any scale. Zooming in to 200% doesn't double the size for 100%.
Have I misunderstood the use of this tool? I want to be able to show a scaled dimension whatever size the printout. A scale bar would work but the grid looked good for this