That calcium level is very high, way too high, which means alk is most likely very very low. The balance of alkalinity and calcium is imperative when keeping sps. The more SPS you have and the more they grow, the more difficult keeping these two in balance becomes. Alk is the most important to test for regularly because it is the fastest level to change (due to lower concentrations compared to calcium and magnesium)
While most montipora's are considered to be relatively easy in terms of SPS, some tend to react poorly in low Alk conditions.
Target levels:
Alk: 7.5 - 9 dkh... and stable
Calcium: 410-430ppm
Mag: 1250-1350ppm
If you are serious in wanting to keep sps and keep this coral healthy and watch it grow, you need to test all 3 of these.... with alk being the most important and most often tested.
I don't have this particular ORA piece but I've kept a lot of SPS and montipora's specifically. That's my experience and the advice I can provide.