It is anything you want it to be

You have allowed tick-tock website to send you notifications I guess. If so, you can clear this permission in your browser settings.

I would think that updating 50.000 Lemmy instances would have a similar performance effect of 50.000 Lemmy users browsing one instance. In that case instance with one user won’t benefit the Fedeverse, but shouldn’t be an issue either.

You can try to clear application cache or to reinstall Jerboa