Vancouver is a city on the north bank of the Columbia River in the U.S. state of Washington and the county seat of Clark County.
The width of the twin quilt is 66 +12 (for the two extra columns of 9 patches) + 4 (for the two extra strips of sashing) =82, which is a bit wider than your target of 78, but close enough. Plus, it's nice to have it a bit too large than a bit too small.
When I went to put the duvet on, it appeared rather large for a twin size. In fact I called and informed overstock that they sent me the wrong the size, so they sent me another one. Apparently the twin size duvets run about 2-3inches bigger than your average duvet, but it looks AMAZING in my son's room!! He loves it!!