HP 3326A Operating And Reference Manual page 29

Data Entry and Mod~fication
The display digit modified with the rotary knob is selected with the right arrow and left
arrow keys. Pressing the right arrow key selects the next least significant digit for modifi-
cation and pressing the left arrow key selects the next most significant digit for
modification.
HP-IB Examples:
"MFY1
"
or
"MFY ON"
Figure 1-12. Modifying Entries with the Rotary Knob