I don't know the Tetra kit, but they are undoubtedly arriving at the CO2 (yes, that's carbon dioxide) based upon the KH and pH readings, which would put your CO2 at 48ppm (unlikely). I think that you have to question the validity of the KH and/or pH readings. Without knowing anything about your tank, e.g.; substrate, additives, etc., my first choice would be to check the pH with another test kit (API or - recently seemingly better - Sera test kits) and, when you do, check both the tap and the tank water. Basically, I'm highly suspicious of the Tetra results but, again, I don't have any experience with Tetra ...other than using some of their other products when I was a kid.
You are probably still cycling the new tank. So, depending on the stage and activity, pH can fluctuate quite a bit.
If you want us to try to guess what may be going on, before you get [better] test kits, post the following info:
- What you are dosing (product and quantity) and how often?
- Substrate type?
- What is your filter setup?
- Cleaning regimen (filter and water change frequency and amount)?
Others may have other requests, so bear with us as we try to gain some focus.