amp gauge and one wire alternator

[65truckowner]

If I read right in the search I performed it says for a one wire alternator and my original amp gauge to work hook the positive side of the gauge to the positive battery cable then the other side of the gauge to the mounting bolt at the alternator. Is this not a direct short? The hot wire from the battery goes through the amp gauge then to the grounded wire at the alternator. This does not seem right to me. What am I doing wrong.