Jeff, you are right. My number was 269, of course it didn't matter.
Finding enough Homasote scraps under a pile of Styrofoam, I pulled up my sidings I started putting in last weekend and put in the Homasote on top of the plywood base. I also added some cork roadbed to make up the difference in height to match the wood. That is tacked down with the glue drying. I'll post a photograph once that project is a little farther along.