The Location’s Magnetic Declination
The angle between True North and Magnetic North, also known as Magnetic Variation.
Enter the Magnetic Declination for this location.  Select West or East for the entry, ignore West or East for a zero declination.
If you do not know the declination, leave the box blank or enter a “?”, DO NOT enter zero.
See the manual for suggestions on finding the Magnetic Declination for a new location.