I would recommend binning the instructions personally, they will be way off the mark for getting the best out of the kit.
If you plan to brew to 23L then I would replace 4L of water with 4L of apple juice.
Check out the link in my signature for brewing a cider kit. I'm generally happy with between 18 and 22 degrees for a cider kit, I only ever use white sugar with ciders/wines and I always allow for at least 3 weeks of fermentation between primary and secondary.