When I made my blocks, I made them on a 10 1/4 inch square including seam allowance. I just extended some of the grass lines or skylines if I needed to when I was doing my appliqué. My block would finish at 9 3/4.
If I add the width of six blocks across that would equal 58.5 inches.
I've cut my lattice strips 3" x 10.25", 5 lattice strips across would be add another 12.5 inches to the quilt.
When you add all your lattice and blocks your quilt should measure 71 in.² .
When you add the two inner borders, your quilt now should measure 76 in.².
So if you cut your final borders 5 inches it will measure 86 in.² instead of 84 as the pattern says. I think I cut my borders 4 inches.
Is ask any questions that you have, it is no problem at all. I hope you were able to understand my explanation. I tried to make it as clear as possible.
Have a wonderful holiday season,