That helps us determine where to start looking for the Leak which ideally reduces our time spent on the Leak Detection - Its a question of whether a diver is needed to check the inside of the Pool or a pipe pressure test.
Losing more either with the pump running or with the pump off indicates a pipe Leak. The first step if you suspect a pipe leak is to do a pressure test. If losing the same amount of water (on or off) points to an inside the pool Leak, & you would need a diver.
Plug the pipes (be sure to turn off the pool pump(s)) and see if you still lose water.
or just run off the main drain (if there is one) by shutting off the skimmer valve(s) typically at the front of the pump.