I had to convert it I think that is around 1/4 cup per 6 cups (6 oz for some reason on coffee makers) . I use twice that but measured in dry beans. Is that really that much?
I think your conversion may be wrong. 60g per liter is 15g for 250ml (which is a small mug of coffee). At least with my coffee 15g occupies most of the quarter cup scoop I have been using. The flavor is good at that strength, but it’s a lot of caffeine. In the ballpark of 200mg depending on the beans and how well your brew method extracts it. 200mg is fine on its own but most people drink a few cups in a day.