The rotary chart printout’s accuracy depends on the block structure, and block size asked for
Imagine your block is based on a 9-patch grid:
But what if you ask for a 10″ block?
When you specify rotary cutting you are asking for sizes that can be easily measured
So if you asked for a Block Size which creates uneven sizes, such as a 10” 9-patch, EQ7 “rounds up” to make the patch size easily measurable. (The actual size, with seam allowance, would be 3. 833333, which would actually be the Template size.) Since this can’t be easily measured, the rotary cutting formula “rounds up” to 3 7/8”, which is easy to measure, but is not as accurate. That’s the very nature of rotary cutting measuring.