The percentage is just marketing BS. The motor max output is 100% no matter what the literature tries to call it. The difference is the nominal rating. A motor is often rated lower than its actual output to get around European licensing and other market restrictions. So a 250w motor may actually be a 500w motor with various limitations imposed in the controller or display firmware. This means you can say things like it's capable of 320% output in certain circumstances where the firmware allows it (like during initial acceleration), but it's max output is governed to not exceed a top speed, at which point the motor is limited to it's nominal rating. You'll often see a motor described as 500w output, but with a bracketed 750W max/peak. If you unlock the settings with programming software or other hacks to bypass the cadence or wheel speed sensors, you can run that motor at 750w all the time if you want.
Every Bafang motor I have seen in a pre-built bike is significantly firmware limited. You can always unlock more power (speed) one way or another, but that can reduce the life of the motor. You have to find out exactly what the motor is in your bike, and then google or search the forums to identify the potential output of it. And to go one step further, until you ride and compare it to another bike of the same class, all numbers are highly suspect. Bafang in particular is known to highly exaggerate their torque ratings, so without a seat of the pants assessment on the road, or an actual head to head performance test, you can't compare them on paper.