Seems average for a coffee-drinking office worker. One for breakfast, one for lunch and one between each major meal (assuming 100mg per cup which would be normal for a middle-roast brew coffee).

But as others have mentioned, it’s hard to control for other factors.

I imagine 300+ mg of caffeine is also associated with a less sedentary lifestyle, for example.

Excess looks like this: https://m.youtube.com/watch?v=UGtKGX8B9hU