Custom Zones Time in Zones Seems Wrong

I’ve set up some Custom Zones as described here: Custom zones for sports

They generally work well. I’ve been using them to plan workouts, and everything about them is great, except that the Time in Zones at the top right of the workout modal seems very wrong

Interestingly, the numbers are different when I’m in Edit Mode (but still wrong):

This only seems to be happening on this page. On the actual activity page, the correct times are displayed (different activity, but same principal):

Any thoughts? I don’t think it’s displaying weekly totals or anything, since within the same week the numbers are different for different activities. Perhaps it’s calculating the time incorrectly?