One's bubble rate is completely dependent on many factors. These include diffusion method, surface agitation, plant load, bubble counter, etc.
Did you calibrate your pH controller? In order to make your CO2 run, you need to set it to operate at a lower pH. For example you can set it to turn on at 6.6 and pump until it reaches 6.0. You could go lower, but that would be determined by the type of fish you keep. Do you have a drop checker to approximate CO2 saturation?
If you didn't know, the more CO2 that gets into the tank, the lower the pH will drop.