Charles Ellicott Commentary Exodus 26:9

"And thou shalt couple five curtains by themselves, and six curtains by themselves, and shalt double over the sixth curtain in the forefront of the tent." — Exodus 26:9 (ASV)

Thou ... shalt double the sixth curtain in the forefront of the tabernacle. —The additional “breadth” was to be doubled back upon itself, so giving a sort of finish to the roof in the front of the structure.