How to calibrate a superdrive's laser for CD and DVD burning?
There is no calibration procedure. Perhaps they cleaned the inside of the mac to reduce dust, but the superdrive units are replaced as a whole by Apple technicians - you get a new drive - not something that is "tuned up".

The only calibration DVD are for running reference sound or visual patterns to help you calibrate a display system for video to ensure dim grey are differentiated visually from black, to focus a projection system, or to check channels or sound levels on an audio system.

Of course there are many cleaning DVD on the market, but I would be loathe to subject my SuperDrive slot loading mechanism to one of those. It could easily get stuck and do far more damage to the drive.