AT Clock Bug?

Ok so I'm watching my AT tick down and I notice that sometimes it ticks down 1 second and sometimes it ticks down 2 seconds, but they both appear to happen within the same time frame.

[Glitchless]

This is because the time updates itself roughly every 1 to 1.5 seconds so sometimes it'll skip 2 seconds but if you get a stop watch you'll see the time goes down appropriately in real time.