https://forums.saltwaterfish.com/t/215685/is-450mg-1-calcium-ok
I'm not sure what unit of measure you're referring to but 450ppm calcium is good if you have a alkalinity level of 12.6dkh or so... but IMO that's running on the high side. Personally I'd shoot for somewhere around 420ppm to 440ppm calcium with 8.4dkh to 11.2dkh alkalinity. Pick a spot and try to keep it as consistent as possible.