A magnetic North arrow on the compass rose shows the variation at your location and the date this recorded with the rate of annual change.
In this example we can see that the variation in 5 degrees West in 2002 and is decreasing 7 minutes annually.
To find variation:
Work out how much it has changed since published and add/subtract that amount.
2002-2019 = 17 years
17 x 7 minutes = 119 minutes. We can round this up to 120 minutes which is 2 degrees.
(We always round up or down to the nearest whole degree).
As it is decreasing we subtract.
The variation in 2019 for this area will be 5 degrees minus 2 degrees = 3 degrees.