The XQ50 has a base mag of 2.7x, and preset mags at 5.4 (2x2.7), and 10.8 (2x5.4)..
The XP50 has what, a base mag of 1.6x? Then presets of 3.2x, 6.4x and 12.8x? I'm guessing they made it so the 1.6x is 1" at 100, 3.2x is .5" at 100, and the 6.4x is .25" at 100..