i dont trust the powdered calibration solutions because you mixing the powder with an unknown variable. I have seen distilled water vary in ph same brand even once was 7.5 and another was 6.8 and with that varience i cant see a powered solution being accurate. and mind you the pen's reading will fluctuate till the solution in the pen acclamates to the solution your testing. usually takes 30 secs to a min to settle. and for now till you can get some pre mixed 7.0 solution I would use your manual test kit to cal the pen and i dont know if you noticed but when calibrating sometimes after removing the screwdriver the numbers jump you need to tweek it lightly till the number stays where you want after removing the screwdriver.