Progress toward fitness award going backwards

Recently the Fitness app started showing me that I was approaching the award for 1000 days with all rings closed. After a while, I realized that my progress was stalled: even though I was recording more days with all rings closed, the "countdown" in the awards section of the Fitness app showed I was stuck at 930 days for about a week.

Today it went backward, to 929 days.

This is the least important problem in the world, but it is kind of interesting.