I would suspect r6 would be 11 or 12% can do the math for both to keep you busy

and I think the plus from sharpened is calced like a haste is its the negs that get different.
Weighted r5 is -50% for 2h speed so base/(base+mod) = 1/ (1 + -0.5) = 1/0.5 = 2x delay
Sharpened is +8% speed so base/(base+mod) 1/(1 + 0.8) = 1/(1.08) = 0.926x
delay
8% haste is also 1/1.08 = 0.926x delay
A 50% slow would be 1*1.5 = 1.5x delay
So sharpened r5 + weighted r5 should be 2 / 1.08 = 1.852x delay for 2h
Beet Da Brat