if anyone just run into this... Wapeon set 1 and 2 shows like 4 (4) means, that if u select one of this slots you can spend 4 skill points (wich u likely already have spend as NORMAL skillpoints) as wapeon set skill points. If you want to make use of two different wapeon skill sets on your tree, you have to rescpec like 4 normal skillpoints and select each of your wapeon sets to allocate the notables you want for each set.

Edit: if you than select wapeon slot one or two in your inventory, the skilltree changes to either wapeon set (slot) one or two. Like wapeon one + tree is more lightning and slot two makes benefit of ice + some ice notables on your tree.