If you are getting 50% leakage and it is coming through into the oil pan, then either the rings or the cylinders are dying. The lower the %, the better, usually you only want about 2 - 5% leakage on all cylinders and a big difference between any two or more is a bad sign. if you are getting 50% across the board, then you might be doing something wrong.
To do a proper leak down, make the fitting is tight in the spark plug hole and that the cylinder you are on is at TDC, depending on the gauge (or at least the ones I have used), you crank the knob to get the needle as close to 100% as possible and the other gauge will read your leak down, if there is a leak, it will be in either the intake valve, exhaust valve or the cylinder/rings. If it is a valve, you can twist the cam back and forth and/or hit the top of the valve (actually the part of the rocker above the valve) and see if moving the valve helps. If it is your cylinders/rings, then you gotta get those fixed. Hope this helps.