I think the brix scale essentially reads percentage of solids directly i.e. 67 brix is 67% solids (solids are almost all sugar).

You really can forget about the numbers entirely and just use the upper read line as long as you hydro your syrup hot.

If you are reheating syrup and want to check it at a temp other than HOT, first read the approx. temp, then look up the proper density on the CHART. The charts are usually in Baume as you can more easily figure the amount of water to add to correct the syrup's density.