This is exactly the kind of pedantry I was trying to avoid by rounding. Fan X moves "15x more" air than fan Y. For every 1 unit of air fan X moves, Y will mov

This is exactly the kind of pedantry I was trying to avoid by rounding. Fan X moves "15x more" air than fan Y. For every 1 unit of air fan X moves, Y will move 1x15 = 15 units. In the time it takes fan Y to move 100 units of air, fan X will move 100*(1/15) units, or 6 2/3rds units. 6.666... rounds to 7.