There would be a difference between adjusting it and calibrating it.
To calibrate, all you need is to run it in parallel with another chrono of known accuracy, and then create a table of factors to add or subtract from the readings yours gives.
Our club chrono came back from Skan (the makers) with a sheet that says, for example, at 1000 fps it reads 2 fps high, at 800 fps it is 1.5 fps high, at 600 fps it is 0.7 fps high, and so on. So any reading can be adjusted with a correction factor.
If you shot a pellet through two chronos in line you could soon see how yours performs against a known one. I would also do a run with the pellet passing the known chrono first and yours second, then reverse them to see if you still get the same result. After all, the pellet will be going a bit slower at the second chrono as you won't be doing the experiment in a vacuum; well, I doubt if you will.