A common practice is to use a pail (s) / bucket (s) of known capacity to measure the gallons from when the pump has cut off to when the pump cuts in. Here again, don't spend time being too precise. If the measure is 3-4 gallons or less it raises our eye brows a bit but if the draw down is 5.5 gallons there is better things to concern ourselves with in life.
The easy diagnosis is when a quart or pint of draw down determines cut off / cut in.
I can tell you from experience it's no where near 3 gallon. If I had to guess less than a gallon.