Hello!

I am learning how to use a map and compass for navigation, and I have been using Be Expert with Map and Compass. So far everything is straight forward and makes sense in theory and in practice, but then I hit a wall on page 126, second and third paragraph. It is about drawing in magnetic north lines on a map using declination. I'm going to take a picture of the page because it is too much to type on my phone :)

I can't highlight or underline anything because it is a library book. Can someone explain this section to me if the map I am using has a longitude line of 44°52.5 N' in the upper margin, and 44°45' N in the lower margin?

Edit: I think I realized my mistake here. Those lines I mentioned would be my latitude lines, not longitude. My longitude lines read identical at the top and bottom of 86° 0' W

But even so, if the longitude lines at the top and bottom didn't line up, say 86° 0' W and 86° 9' W, how do I add magnetic north lines using a meridian, and which longitudinal lines are considered meridians?