The numbers corresponds declination values eastwards from the true North. The chart values give the mean value of declination over an area approximately 50 km x 50 km, but real declination values, as measured at a given place, may differ several degrees from the chart values. The declination is slowly changing from year to year due to the secular variation of the geomagnetic field as whole. The reason to this change is the slow fluid movement in the Earth's liquid core in the depth of 2900 km. The annual rate of the secular variation in declination is 0.1 degrees to the East.
Inclination gives how many degrees geomagnetic field vector deviates from the horizontal plane.
In Finland inclination varies between 73 deg and 78 deg from south to north and its annual change is 1'. The former value occur at the northern geomagnetic pole which is located in Canadian Archipelago approximately at 78 N and 100 W, some 1000 km south of the true North Pole. Its southern counterpoint lies near Antartica about 400 km south of the Australian coast. The map shows the mean distribution of the horizontal component of the geomagnetic field vector in Finland. The direction of the H-vector determines the orientation of the needle in a magnetic compass.