First lap 1 second faster than cumulative time

been meaning to write about this one and i unfortunately don't have a photograph to give exact details, but this is it:

i have my watch set to auto lap (although i think this also happened when i was doing a manual lap a couple months ago): when the first lap completes (1mile), it typically is 1 second or so faster than the cumulative time.

eg, today, i mentally noted it showed 9:06.4 for the first lap, but the cumulative time was 9:07.7

this is pretty typical and consistent. not sure if it's a bug or what. Garmin Connect shows my first lap as the cumulative time. (as does Strava)

not a big deal, but an odd bug...