Interesting observations. It ("the exit count that the Garmin maps tell you do not match the pointed-lines radiating out from signs") has occured much too frequently with me to be a one-time fluke.

I'm not using a Nuvi, I'm using a GPSMAP 76CSx, but I am using the same mapping software that comes in the 350 and 370. I'm also a little suspicious that this is all happening within a certain region, from Glasgow north to Loch Lemond, maybe the map/database updates here are different.