When I woke this morning my Descent MK1 told me I'd done around 80 steps since 12am which is about right. When I synced with GCM, GCM told me I'd done over 1,000.
As the day has progressed GCM and GC both report around 1,000 more steps than the Descent. GC actually shows 995 steps between 12:30 and 12:45am! My sleep data is wrong, too. I don't sleep walk!
After my run this morning just before syncing completed, GCM showed the correct number and then after syncing it was wrong again.