While the vehicle is executing a mission, the user can increase the vehicle’s speed by raising the transmitter’s throttle stick to between 75% and 100%. At 75% the vehicle will remain at it’s configured speed (i.e. WP_SPEED or CRUISE if WP_SPEED is zero, versions of Rover after 3.5.1 use only WP_SPEED), this linearly increases to the vehicle’s maximum speed as the pilot’s throttle stick reaches 100%. https://ardupilot.org/rover/docs/auto-mode.html?highlight=speed