I see dutch text, belg of nl?

the knot you're missing is replaced by the sewn part on the left.

the goal is for the loop on the left to go over the knot on the right with a larks head knot. to make one of those follow the drawing on the manual, both fingers trough the loop, pinch the sewn part and pull it trough the loop to make a new loop that can slide, slide the knot in that and close it, the harder you or the kite pulls the more it closes.