Just go slow. Double check the results first and if possible cross reference with other test kit.
350 Calcium is at the low end. 11 is max for alk tho I believe. Dose slowly and the calcium will displace the alk (or the alk will slowly get used up by the tank) and should bring things back into balance. Should figure out why this happened tho. I shoot for 400 calcium, 8-9 alk and 1300-1500 mag.