My Doctor Has Me Taking1 Tablet By Mouth Twice Daily

My doctor has me taking1 tablet by mouth twice daily of Calcium 500mg/Vitamin D 400unit Tab. He has also taking Calcium Acetate 667MG Cap -- 1 tablet by mouth daily. Are these two Calcium tablets the same? How are they different? The latter -- Calcium Acetate 667 MG is the tablets that I shall take once the Calcium 500MG run out. I don't want to be taking too much calcium. Would you advice me with your expert opinion please.