Less than 100mg caffeine intake for keeping hippocampus volume

The quest for finding the perfect dosage of caffeine/coffee for me continues. My recent position is influenced by an article I read that looked at caffeine consumption and hippocampus volume. The results were that subjects with consumption less than 90mg caffeine and more than 400mg caffeine had greater hippocampus volume than those in the moderate consumption group, 100mg-400mg. Thus inorder to achieve the benefits of coffee and not compromise sleep, meditation, etc, I think it further supports my habit of sticking with at most 1 cup of filtered organic arabica bean coffee, and not finishing up the whole cup. I also take caffeine breaks of 4 dats up to a week once a month. It's likely that I will stay under 90mg of caffeine per day. It would be nice to have a coffee machine that measured caffeine. https://www.sciencedirect.com/science/article/pii/S0006291X07005682 Biochemical and Biophysical Research Communications Volume 356, Issue 4, 18 May 2007, Pages 976-980 Biochemical and Biophysical Research Communications Inhibitory effects of caffeine on hippocampal neurogenesis and function