Power Scale acts like grayscale, and ramps the Max Power setting from Min Power to Max Power based on the percentage - It acts like a slider between min & max.
It doesn’t change how Min Power is interpreted by your controller. Ruida calls it “Min Power”, and other controllers often call it “Corner Power” - that’s probably the easier way to think of it. When the controller slows to it’s “Start Speed” (10mm/sec by default on Ruida), it uses Min Power only. As it ramps up to the chosen speed, assuming it’s higher than the Start Speed setting, it ramps the power up to Max Power. If you never go above Start Speed, you’re only using Min Power.
A CO2 glass tube has a firing threshold called the ionization point - that’s where the gas in the tube is excited enough to start lasing. The larger the tube, the more energy it takes to hit this point, but 10% of the wattage of the tube is a good ballpark, so I’d expect yours to fire as low as 5%.