system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What happens when T.V. shows the first second of a commercial, then switches to a new commercial?
gpt
It's because the local station is list a second late in starting the local commercial.

The network will have certain commercial spots that are for local affiliates/cable companies to air ads that they sell. But, just in case the local station doesn't have anything for that, the network will have a commercial running.

When it works smoothly, you don't see it, because the local ad completely covers up the national ad. But if the local channel is a little late in starting the ad, you'll see just a bit of the national ad first.