If you use a setting a grid value that is too large the dots disappear. That max number is 24 for US numbering system. Not sure what the cm max number is but it might be 64.
Not sure it's necessary to worry about it either way. I seldom specify numbers for sizes as opposed to simply dragging control/section edges. shift+ arrow key makes minor size adjustments, ctrl+arrow key makes minor move adjustments, arrow keys alone make slightly greater adjustments. Let's say I wanted a group of controls to be all at the same top setting. I can choose one, copy its top setting then choose all desired and paste in the copied number and they'll all move to that value. So my point is, I don't need to worry about measurement units. AFAIK, if you want to work in cm's you have to have the correct regional setting for numbers but also a valid grid value for that system.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.