I'm too ill right now to go to the other room and rummage in my quilting bookshelves, but it looks suspiciously like the charts from the Better Homes and Gardens quilting encyclopaedia. If so, check it very carefully. The charts in that book are chock full of errors, as I discovered the hard way when following them to make isometric triangles. It doesn't look like the sort of site to breach copyright, though, so this is rather odd. Has anyone gone through and checked the charts to see that they're all accurate?