RAM 1500 Owner's Manual page 416

414 STARTING AND OPERATING
gear in the instrument cluster, and maintain that gear as
the top available gear. For example, if you are in DRIVE
and are in third (direct) gear, when you tap the shift
lever/switch one time in the (-) direction, the display will
show 4 (ERS 4 is direct gear). Another tap down (-) will
shift the transmission down to ERS 3 (the added under-
drive gear). Once in ERS mode, tapping ERS (-) or (+) will
change the top available gear.
Column Shift Lever