I must have half a dozen ESCs from a variety of manufacturers and they all calibrate their throttle settings in the same manner. (Remember that Futaba use a reverse throttle signal). The procedure can be repeated as many times as you like, effectively deleting the previous setting.

1. ESC off, TX on with throttle at max setting.
2. Power ESC, ESC beeps, quickly move throttle stick on TX to minimum, ESC beeps again, throttle range set.

If the ESC is ever powered up with the throttle stick above previously set minimum, ESC will beep continuously and motor will not arm - moving the throttle trim up accidentally can cause this.

Don't forget to have the model securely fixed down and keep fingers well away from prop when setting the ESC. Mistakes are easily made and it's no joke to have a model start up when you're not expecting it (ouch!).