Hal uses these paces as a measure of your effort on an uphill. He cannot predict how steep the hill you choose will be, so when you’re doing hill repeats, use those paces as effort references. For example, if Hal says to run 8:00 min/mile, you may be running 10:00 min/mile on a 4% gradient, but it should feel as if you’re running 8:00 min/mile on a flat road.