Hi Robert, the tester does not know if it is connected to your battery or the alternator and only measured the voltage it detects. The Alternator LED is illuminated on your bench test as it has measured an indicated voltage of 13.2V, although for an accurate voltage reading you may want to double check with a volt meter. With the battery connected to the vehicle, the alternator should be outputting approx.  13 – 14.8V to the battery to allow for drain on the battery from the normal electrics load to ensure that the battery will always have a static voltage of around 12-13.00V to allow the vehicle to be started. Voltage does not itself indicate the overall condition of the battery and if you have any starting issues you might want to consider having a shunt/ load test carried out.