Width Not Quite Right

At this risk of missing something and/or typoing, here is studiopress’s “add this to your css” list:

/* Column Classes
    Link: http://twitter.github.io/bootstrap/assets/css/bootstrap-responsive.css
--------------------------------------------- */

.five-sixths,
.four-sixths,
.one-fourth,
.one-half,
.one-sixth,
.one-third,
.three-fourths,
.three-sixths,
.two-fourths,
.two-sixths,
.two-thirds {
	float: left;
	margin-left: 2.564102564102564%;
}

.one-half,
.three-sixths,
.two-fourths {
	width: 48.717948717948715%;
}

.one-third,
.two-sixths {
	width: 31.623931623931625%;
}

.four-sixths,
.two-thirds {
	width: 65.81196581196582%;
}

.one-fourth {
	width: 23.076923076923077%;
}

.three-fourths {
	width: 74.35897435897436%;
}

.one-sixth {
	width: 14.52991452991453%;
}

.five-sixths {
	width: 82.90598290598291%;
}

.first {
	clear: both;
	margin-left: 0;
}

I’d probably just copy/paste those width values into the plugin’s css, since you can see how some of them are off by ~2%, and some of them have rounded percentages, etc.

Ultimately, it looks like the 2/3 width is calculated in your plugin by adding two 1/3 together, but is missing the middle margin ~2.5% that would also be in between two 1/3 to make up a 2/3-sized block – not sure if that’s factored into the others.