Isn't this wrong? At 100 ranks of air and 100 of MjE, shouldn't 10 seconds be reduced by -6? Or am I misunderstanding your chart?
The maximum possible roundtime reduction that can be attained with this spell is a 60% reduction of the original roundtime. With this maximum reduction, the end result would be 40% of the original roundtime (e.g. a 10-second roundtime would be reduced to 4 seconds, and a 20-second roundtime would be reduced to 8 seconds.) This maximum benefit is attained when MjE ranks + EL:Air ranks = 200.