Big question: Do you own one yet?? If you do, all this information should be very clear. If not, then buy one, you won't regret it, and everything posted here should be Crystal clear.
I see from another thread you have ordered two Fatboys. Excellent. Like I said, once you have it in hand, all this will make sense. Don't overthink or worry about things, DE shaving is a breeze.
Fast forward to 2:00 to 2:45 for specific Fat Boy info. Watch the whole video for Enabling Action. (Thanks to @mantic for the informative content!)