The manufacturer is clueless. What make of saddle is it? Move the saddle back. Pay no attention to where your knees are. Just move it back until you can lift your hands off the hoods while riding without sliding forward on the saddle. Hopefully you have a setback seatpost. Your weight should be on the saddle and the pedals, very little on your hands. Also of course the saddle should be approximately level and at the usual height: with your heel on the pedal, your knee should lock out with no weight on the pedal.