It's all to do with the TIME you will be exposed to the wind. (CARP calculations for any ex-tac airdrop boys or firefighters or anyone else who drops stuff from airplanes)
60 kts wind = 1nm/min
30 kts = .5nm/min
divide alt to lose by normal descent rate (usually 2500 fpm for 3 degrees/idle thrust) and multiply by wind factor related to the above.
i.e. 15000ft to lose = 6 min; with 60kts tailwind = 6x1 = additional 6 nm required
30000ft to lose = 12 min = additional 12 nm required
Normally this is a tad too much as the wind usually decreases as you descend.