The question is why?
6 weeks vs 4 to 8 weeks.
It is strange writing.
How about, the voyage is expected to be about the same.....
I guess 6weeks is the max speed vs 4 weeks.
“6 weeks vs 4 to 8 weeks.”
20 days = 2 weeks, 6 days
40 days = 5 weeks, 2 days
So sails would take anywhere from “twice as long” to “just longer than” a 100%-fuel-powered trip.
That “ton and a half” fuel savings is really gonna pay for itself.