3 days of screen time? Mmm OK. Sure...
Sent By An Idiot With A Phablet!
I'm sure it is to be read as 3 days overall with ~5 hours of screen-on time.
I have no problems with use of the phone like that. If some people like WiFi-only, all push/sync disabled or manual and fairly light usage to eke out close to 72 hours and that's their preferred usage pattern, more power to them.
I only get a little irked when this is boasted as if a typical user who keeps their push/sync on all the time and is a moderate+ user with substantial mobile data usage can achieve close to similar figures.