what is the purpose of "smaller_speed_factor "?

vmax_junction = _MIN(nominal_speed, previous_nominal_speed);

      // Now limit the jerk in all axes.
      const float smaller_speed_factor = vmax_junction / previous_nominal_speed;  
     
      LOOP_XYZE(axis)
      {
        // Limit an axis. We have to differentiate: coasting, reversal of an axis, full stop.
        float v_exit = previous_speed[axis] * smaller_speed_factor,
              v_entry = current_speed[axis];

if (previous_safe_speed > vmax_junction_threshold && safe_speed > vmax_junction_threshold)
        vmax_junction = safe_speed;