What’s ~200m of climbing between friends?

After reviewing my previous 40km stats following this morning’s 40k effort, I was pleased to see that despite having done 49k yesterday (the 40k route plus a loop up to Dornoch Tce and back via The Mater), I only dropped 12 seconds.

That said, I am utterly bamboozled by how inaccurate my Garmin Edge 705is for altitude. Just have a look at these numbers, remembering that I am actually riding the exact same course for each activity:

That’s with the elevation corrections enabled, too, so I would expect that Garmin Connect would be using accurate topographic information rather than some random stuff.

Anybody know why this might be?