rokija,
Don't confuse "airspeed" and "groundspeed". Performance speeds are all based on flight within an airmass, or more simply flight with ZERO wind. Your 69 knots max glide distance airspeed (if that is what the flight manual calls for) is probably the speed for the best range you can get in autorotation at the proper rotor rpm. It is up to the pilot to understand that with a 10 knot headwind you will not cover as much ground at 69 KIAS as you would with zero wind or with a 10 knot tailwind. If the speeds were derived correctly, any increase above that 69 knots will not increase your glide distance as your rate of descent will increase giving you a steeper descent angle. Slowing the acft down will also give you a steeper angle, but to a point (min rate of descent airpseed) will give you a progressively slower rate of descent.
Next time you are out flying on a calm day, try it out. Get up to 2000 feet AGL or so, enter an auto at max range airspeed with rotor rpm at the proper setting (usually bottom of the green) and stabilize. Look at your glide angle then slowly accelerate a few knots at a time and see what happens to your "circle of action". It should move closer to the acft. If you decelerate back to Min ROD, the circle of action will again move further out. You will also see a change of your circle of action with a change of rotor rpm. Once you see how far the acft glides on a no wind day, just understand that with a headwind you won't go as far and with a tail wind you will glide further, but the bottom part of a tailwind autorotative landing is not the most desireable way to land.
Cheers
Mark