But seriously, to adjust the supply, disconnect the game board, and run the power supply unloaded. It's a linear supply, so you can do this. Put your meter on one output voltage and adjust the pot that corresponds to that voltage, to bring it into range. Repeat for the other two voltages. Then, connect the boardset and power it up. Use your meter and readjust all the voltages to bring them back into range, as they will have changed now that there is a load on it.
The only reason for the first step of running the supply unloaded is to prevent damaging the game board by having one voltage cranked up too far at first. You could probably also just turn all the pots all the way down to start and be fine too.
-Ian