Quilting Question- Sewing with Jellies

Hello,
I am making my first quilt using the "lawnchair quilts" free pattern from the Moda Bake Shop blog.  The pattern calls for joining three jelly strips together: solid-print-solid.  The pattern states that my finished width of this combo should be 6 1/2 but mine keep measuring 6 1/4?  Did I do something wrong?  I double checked my SA and it measures 1/4 and I double checked my jelly strip width and that seems Ok too??  Any help would be greatly appreciated Hopefully I didn't make a dumb mistake! Ha Ha.

Since you wrote that you've already checked that your jelly roll pieces are 2 1/2" square and your SA is 1/4", there's something else going on that's throwing your seams off.
Double check your needle position. Maybe it's moved over a tad from a previous project?