Great Northern Slab (descending)
Several abseils were required to descend from the route. The first abseils went without problem. On the final abseil, instead of placing the mid-point of the rope at the anchor, we rigged with one of the end markers at the anchor. The ends of the rope were marked with black stitching (by the manufacturer) in a similar way to the middle marking. This left one 5m long end and one 65m long end. We did not tie knots at the end of the rope for this abseil, as we expected to reach the ground. My partner attached to the rope as normal, and noticed the error only after detaching from the anchor. She clipped back into the anchor and we pulled the rope through to the middle marker to fix the issue.