On-point blocks are set diagonally. Therefore their horizontal and vertical measurements are also on the diagonal: through the block’s center. If you measured the full width and height of the quilt you would measure across the on-point blocks, not along their edge.
It is this horizontal and vertical measurement through the block that appears on the “footer” information at the bottom of printouts. This is different from the block’s edge size. For example:
Formula: Block edge measurement x 1.414 = Block diagonal measurement
Example: 6″ x 1.414 = 8.48″
Don’t worry when you see a larger size given for on-point blocks. It’s the (diagonal) horizontal and vertical measurement, not the block edge length. When you print, click the “Use size from quilt” checkbox, and trust that you will get the pattern or block sized as you have predetermined it on the quilt layout.