IBM S544-5343-03 - Manual (Page 31)

Use the Value key to scroll through a list of acceptable values for a
menu item. Press the Value key once to scroll forward one value.
Press and hold the Value key to scroll more quickly through the list
(especially for numeric values).
Note: To select a new value, press the Continue/Enter key when the
value is displayed in the message display area. An asterisk (*) appears
next to the value, indicating that it is now active.
Use the Shift key to reverse the order in which you scroll when you
use the Menu, Item, or Value keys.
Chapter 2. Using the Operator Panel 11