Doing the 10% inc in my head, and assuming the 80km was the product of increasing mileage each week I'd still not get Dec past 110km, and that's without a drop back week anywhere, so allowing for that I'd be looking at getting to 105km max from 80km prev month.
It's only 15km (9 miles) diff so about ave .7 miles per run assuming a 3 run per week approach I think.
I don't get the formula either I'm afraid.
Doing the 10% inc in my head, and assuming the 80km was the product of increasing mileage each week I'd still not get Dec past 110km, and that's without a drop back week anywhere, so allowing for that I'd be looking at getting to 105km max from 80km prev month.
It's only 15km (9 miles) diff so about ave .7 miles per run assuming a 3 run per week approach I think.
(I'd have to write all of it down to be sure).