It might also be useful to point out that it's not any kind of plan for the Battle of Antietam. It was issued on Tuesday 9th, for Wednesday 10th to Friday 12th inclusive, and was found on Saturday 13th; if it's a plan for any battle it's for the Battle of Harpers Ferry.
It's a plan for one part of the Maryland Campaign, and was useful, but by the Battle of Antietam it was hopelessly obsolete.