That's NR, not NMN. Also, the daily Elysium dose of NR is 500mg, much less in proportion to body weight than what was fed to the mice in this Harvard study.
Added: Thanks to jclos below. The human-mouse-equivalent NMN dose would be 1/12th, 25mg/kg of bodyweight/day.
Keep in mind that there is no 1:1 mapping between mg/kg/day for mice and for humans due to difference in metabolism. http://www.ergo-log.com/calculatethehumandosage.html gives a couple of useful formulas to calculate the actual dosage for humans and it's much more reasonable.
Having done some ECLSS stuff it takes about 13 mice to equal metabolic load of a human. This does not add up if you use mass alone, but comes out pretty close using volume/surface area metric.
Added: Thanks to jclos below. The human-mouse-equivalent NMN dose would be 1/12th, 25mg/kg of bodyweight/day.