It could be insightful to fool around with Randy's calculator and add the exact amount of alk supplement suggested to bump up kH 1 point (i.e. from 7 to 8) and see how the two different tests display the before & after numbers.
If you could get your hands on a verified calibration sample, that could eliminate ambiguity. Getting a reading from a good 3rd test like Salifert could help clear things up -too they don't cost much. Also, getting an experienced person to run one of your tests, if possible, can help tease out any human error.
It seems like there are difficulties or confusion on the technique or procedures associated with some of the Hanna tests I've read about. Not sure what, but there is talk of fingerprints, getting all the powder out of the packet etc. Not sure if that's a possibility in your case.
If a fresh Red Sea kit & a Salifert kit were in general agreement, I'd go with those numbers. A few the tenths of a point margin of error are to be expected in any hobby grade test kit and shouldn't be a worry.
