the test kit was just to compare just never seen 8.4 thats ocean ph.I just dont trust hanna at all.Had way to many problems with them.took 4 of them back.ended up with another band they took the hanna back and gave me credit.just not a big fan.and you can test the accuacy of a strip kit with your 7.0 solution and see how it fares.... its good to get a base line.