The calibration is for the meter to confirm the probe is properly reading the solution. You should calibrate your meters every month to ensure accuracy. Once you use the solution, you toss it out. They sell bottles of it at the store for about 25 bucks. You will not technically set anything, have the probe soak in the solution for a few minutes until it has settled on a value, then follow the directions to calibrate it. The calibration will adjust the the meter to proper value if it is not reading the value indicated on the solution bottle. I'm not sure how you cap is, but i always leave a little solution in my cap so it is sitting in that while not in use.