@sr123... You may have a different edition (there are quite a few!) with revised diagrams, perhaps. It's definitely 15-16 in my copy (2nd edition), step 20 is "turn over", but you're right about the procedure.
@sandy: You need to make sure that the fold in step 15 results in a straight line down the centre of the model, if you see what I mean. In your picture, the bottom point needs to swing slightly to the right so there is no pleat on the left. It should look exactly like the diagram. Then its as Sr123 says. It should all satisfyingly pull into place on the right, providing you've been accurate. I avoid making any sharp creases until everything is lined up nicely.
You may want to adjust the triangular flap on the bottom of your picture (the fold made in step 14) so both corners are lined up, this will give a cleaner result on the tail. I've found its often more important to get creases lined up corner to corner than worry about the end of the flap
Hope this helps!