Canopy
Just to get it right, mc during let's say 24h saw 9 S rank and 1 SSS rank. The refresh rate was once a minute so in 24h there were 1440 refreshments. That means probability of getting S rank is 9/1440 = 1/160 - every 160th person get S rank.... And every 1440th person get SSS rank.... (he might got lucky for SSS rank but still the prob shouldn't be that low high)