The motor break-in feature on the ICE helps to determine how many amps your motor is "pulling" from the ICE. If the brushes are seated well on the comm, and the comm is round, generally speaking, the motor will pull more amps from the ICE. This can be used as a "rough estimate" to see if it's time to cut the comm, clean the motor, and/or install new brushes.
Keep in mind, this is not a dyno though. This does not give you how much power your motor is generating. In fact, if you grab a hold of the motor axle, during the test, you'll see the amps go up.
But for the most part, with no load, you can use this as a quick test to see if your motor is in good shape.
Set your break-in voltage to be 3.0V. You should see anywhere from 2 amps to 10+ amps. More is generally better. (If it goes over 10 amps, the ICE will stop the test since it thinks something is wrong.) Most motors properly tuned (or new) will be over 5 amps. The average motor I've tested will be 5-7 amps range.
One motor example: I ran a P2K2 motor about 40-50 runs and it fell to 2 amps. The motor was performing badly on the track. After a comm cut, cleaning, new brushes, and break in, it went to 6 amps, and the motor performed much better on the track. So as you can see, this amp draw number can give you a quick idea of the condition it's in.
Now if only there were some inexpensive load dynos for sale... that would rule.