Alkalinity

[Seriak]

So my tank is a couple months old now and I have done a 15% water change every week for the last month. I finally got around to measuring my alk and Ca. My Ca was between 400 and 450. (I didn't bother with the precision test) My ph is 7.8-7.9, but my alk is in the 3.5 dkh range. I did the test twice using my Hanna kit. Now does that alk seem plausible or should I buy a different test kit and test again before I go dosing anything.