You can do this on the climbing wall, as well, but the systems board is set up to have holds mirrored left/right so you can have the exact same pinch at the same height with your left and right hands. Choose two pinches and do the recommended number of pull ups on them.
Make this easier by using better pinches and/or jumping up into the top of a pull up position on the pinches and then slowly lowering yourself down. These are called “negative reps”.
Make this harder by choosing worse or smaller pinches.