On the original post it would seem you has deviation and variation confused, deviation does not increase or decrease annually in minutes. It is set by the errors on various points on the boats steering
compass and noted on the boats deviation notes ( normally set out as a graph but referred to confusingly as the deviation chart ! and it relates only to that vessels compass)
The annual change of variation of magnetic compared to true north is found on the charts
( maps ) compass rose and varies between you position around the globe.
The - and + is a misnomer , the variation is east or west , then you apply the phrases (noted on others posts ) depending if you are working from the nav table to give a course to steer to the guy on the helm
or you have taken a bearing when on deck
and need to place that on the chart to find your position on the chart
Hope that helps
Sent from my iPad
.......i apologise for the auto corrects !!!