5.09 is pretty low. But yes the above are correct. You have to read the small writing at the very bottom of the card. It is written there. I missed it the first time also.
I would not agree with that statement. If you mess up the slightest they are way off. But I know people that use API for alk and their tanks are perfect! Sps look the best and have crazy growth.
I know people have had some issues with the Hannah testers so take the reading with a grane of salt
I use API all the time for more of a daily tester and use my lamotte test kits to verify my API test kits are still reading correctly. So I have found the API kits are pretty close as long as they are not old, I replace my API kits yearly. I have had more problems with salifert test kits than API, so far 2 bad salifert alk kits so salifert no more, maybe just a run of bad luck but I can't risk some of my corals on a bad run.
Others have had good luck with salifert and swear by them but I just don't trust it anymore.