Caffeine is generally recognized as safe by the US Food and Drug Administration (FDA) at a use level not to exceed 200 ppm (0.02%) in cola-type beverages for the specific intended use of flavor (21CFR§182.1180). Caffeinated beverages, like coffee, have been consumed for centuries. Current estimates suggest that the mean consumption of caffeine (all ages) is 165 mg/day, ∼105 mg of which is associated with coffee consumption (Mitchell et al., 2015)… More at ScienceDirect.
So, coffee is safe in any quantity. Excellent. I think that’s what it said.