So I hooked it up to a good lead acid car battery and measured values at the terminal clamps. Ammeter did move but got inaccurate, however constant, values. Around 4mA regardless of the Amp selector position. Here's what I got:
6V/6A - 4.21mA/12.51V
6v/2A - 4.22mA/12.52V
12V/6A - 4.97mA/14.54V...