Slices burned

Hi everybody.
I have 13 slices burned on my All Time page and 14 slices burned on the last 30 days page. How can it be ? Do we lose slices burned over time ?

I had a very similar thing. If you have ridden a couple of KMs/miles, but you do not save the ride, they still count for the last 7/30 days and they count for your weekly total. They do not count for your overall all time.

Thanks M.B.
It makes sense.