Do you mean Deviation or Variation. Either way from AP3456
Variation is measured in degrees and is named East (+) or West (–) according to
whether the North-seeking end of a freely-suspended magnetic needle, influenced only by the Earth’s
field, lies to the East or West of True North at any given point.
A useful mnemonic is:
"Variation East, Magnetic least,
Variation West, Magnetic best."
For Deviation:
The angular difference between the direction of Magnetic North and that of Compass North,
and therefore all Magnetic directions and their corresponding Compass directions, is called
Deviation. Deviation is measured in degrees and is named East (+) or West (–) according to
whether the North-seeking end of a compass needle,under various disturbing influences, lies to
the East or West of Magnetic North.
I have always used + East and - West.