What I Understand:
- Snap Shot & Improved Snap Shot feat allow you to threaten up to 10 feet from you or 2 squares on combat. You can make an attack of opportunity to any hostile entering and leaving that space.
- Combat Reflexes let you make multiple attacks of opportunity up to your Dex mod.
If a hostile enters your 10-foot threaten area, you get an attack of opportunity. Regardless whether the attack hits or not, the hostile presses on to your 5-foot threatened area. Are you allowed then a secondary attack of opportunity at the same hostile for crossing both your threatened zones?
PS: I would have added Greater Snap Shot but the feat in the PFD20 site did not specify if this feat also allowed an additional 5 foot square to be threatened.