See screen shot; the intended values for the custom disc are reflected incorrectly. Minus 6 PP is actually raising the cost by 4 (instead of lowering by 6) and the +% damage is not actually reflecting the proper increase.

This is actually the way it works. Crafted PAs and Techs have different base values than the PA/Tech they are overriding, so a Potency +0%, PP Cost -0 lv15 Cerberus Dance /C would have a Potency of 2280% and a PP Cost of 40.