I have a copy from my water Co. and all I can see is Hardness (mg/l 66 to 190
or Hardness ( grains per gallon) 4 to 11 is this what you mean?
Yes but this isn't precise enough for us to use.
If you have an API Ca test kit you can estimate Mg using this formula.
((17.86 x dGH) - (2.5 x Ca ppm)) / 4.1 = Mg ppm
(ppm dGH - (2.5 x Ca ppm)) /4.1 = Mg ppm
Some lab tests are not so cheap!
You could also get a JBL Mg test and test for Mg. It is pretty accurate. It maxes out at 10 so if you find that your Mg is over 10, better to dilute the aquarium water: Half RO half aquarium and just multiply your results by 2.