Every plant hanger pattern on this site has the same shape: a ring, a gathering wrap, a set of arms, a net that holds the pot, a second wrap under the pot and a tassel. The pattern lists them from the top down, and every number in it comes from the cord size, the pot and the hanging length you asked for.
The cut list
Working cords are the long cords that do all the knotting. Each one is folded in half through the ring, so 8 cords give 16 strands, and the strands divide into arms of four: two working strands on the outside that tie the knots and two filler strands in the middle that the knots are tied around. The cut length is the sum of every section's length times how much cord that section uses (4 times for square knots, 3.5 times for a spiral, 1 for plain cord and fringe), plus a little for the wraps and the trim, doubled for the fold and rounded up to 10 cm. Cutting all working cords the same length is deliberate: the fillers of one section become the working strands of the net, so no cord can be short.
The two wrapping cords are separate short pieces for the gathering knots. Their length is the number of turns times the circumference of the bundle, plus tails.
Arms
A section marked "square knot sinnet, 12 cm, 12 knots" means twelve square knots tied one below the other on each arm. The count comes from the cord: a square knot in 4 mm cord is about 1 cm tall, a half knot half that. If your knots come out taller or shorter, follow the length, not the count. A gap is simply plain cord; a spiral is half knots all tied from the same side.
The net
The net is one row of square knots per arm, each knot tied between the two right strands of one arm and the two left strands of the next. The pattern gives the drop (how far below the previous row the knots sit) and the spacing (how far apart the knots are around the pot). The spacing is the pot's circumference divided by the number of arms, so the net closes around the pot at its widest point and the rows lie on its side. A three-row net on a 13 cm pot with a 4 cm drop covers the top 12 cm; the strands then run under the base to the bottom wrap. Put the pot in before tying the bottom wrap to check.
Hanging length
The hanging length is measured from the top of the ring to the end of the tassel: ring diameter, top wrap, arm sections, pot height (the net wraps the pot), bottom wrap and tassel. The designer keeps it within 10% of the length you set. Change the pot size or the length on the designer and the whole pattern is recomputed.