How much Ca+ to add at once?

[danny zubot]

I was sitting at around 280ppm then added one capfull and two hrs later I was at 440ppm

Thats what I was wondering because it says on the jar to not raise by more than 12ppm in one day. I'm still sitting at 260 ppm as of yesterday even after adding about a half a jar over the past week. Maybe the powdered Seachem Ca+ just sucks.
I added a double dose last night as well as ALK buffer, I'll test when I get home and see if it is higher. My corals are doing well but my Ca+ has been low since I started using the IO salt from the Boxing day sale.