Looking for some opinions on water chemistry, Been having trouble with nitrate levels so I bought salifert test kits and tried again.I made new water at got strange results.

PH 7.7
DKH 14
Phosphate .25
Calcium 520+ (extapolated the scale and I think it is about 580)

All other values were in spec.
Used just tap water and denitrifier.
Made water to spec using Kent reef salt. Let the water sit for 3.5 hours took readings and got the results I listed.

Is it the tap water or the reef salt or some combination. Also open to suggestions as I am new to the hobby and still very humble.
Just don't want to kill anything