That's a test for water hardness. You need to test for calcium before treating. Actually need to test for everything before treating. I recommend actually getting the liquid tests as the strips are not that accurate. Maybe take a water sample into your LFS
and ask them to test for everything so you know what exactly your water parameters are. Calcium levels need to be above 400.
In all reality, I would see if the store would take back the flower pot and let you pick out something more hardy. When those flower pots die, they can crash your whole tank. They are definitely not for beginners at all. Like I said before - even people that have had tanks running for years can only keep the flower pots alive for about a year and their water is PERFECT.