Sounds about right. 50% on a typical 12v battery is about 12.06v.
For batteries built of multiple standard cells, 2.01-2.05 volts per cell is widely accepted as the 50% mark, and 2.1 volts/cell is 100%. I'd call it an even 24v for 50% on 12 cells, since it's only a yardstick anyway. No need to be over-precise.