No exact point
There is no exact point. It depends on many variables.
To prove it, put in an approach in the box. Note the decel point. Then assume that you're doing a stabilized approach (Vapp at the FAF) and enter the Vapp speed restriction at the FAF.
Note what happens to the decel point - it moves so that you hit it sooner.
Denti - the decel point will be on your screen in HDG, but flying over it won't activate.