Magazine Ad & Billboard

The magazine I have decided to make an ad for is Vogue. I have researched the advertising specifications for a Full Page and this is what is stated:
Bleed 8 1/4" x 11 1/8"
Non-Bleed 7 x 10
Trim 8 x 10 7/8
Live 7 1/2 x 10 3/8

The formula give in class to find the bleed and margin amount:
bleed amount = bleed - trim = bleed size / 2
my math:
8.25 - 8 = .25 / 2 = .125 width
11.125 - 10.875 = .25 / 2 = .125 height
margin amount = trim - live = margin size / 2
10.875 - 10.375 = .5 / 2 = .25 height
8 - 7.5 = .5 / 2 = .25 width

http://www.condenast.com/brands/vogue/media-kit/print/ad-specifications