Notification bar wifi shows 2 bars but Settings shows 4

Can anyone explain the inconsistency? The Settings reading seems to be correct, because there isn't a lag when I play online content, but its disconcerting to see the low bar reading in the Notification bar. This is on a Galaxy S5 Active running Lollipop and happens wherever I connect, whether it be at home, at work, at a coffeeshop, etc. See image . Thanks!