Hi Comrade,
50 here is a percentage of the target’s clock, so 50 is 0.5 * 6.25e-8s. If I remember correctly, the minimum step is 100/256 (roughly 0.4%). Keep in mind that this is just how long you’re turning on a mosfet for, not the glitch itself, so small glitches usually won’t be large enough to drop the voltage at the target’s Vcc pin.
Alex