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.
At 39 inches wide by 75 inches long, a twin mattress is the smallest bed on the market. Its compact footprint means it's ideal for children and single adults. A twin is also great for individuals with small living spaces, such as studio apartments.