Wises clarification

Rules state

"Once you’ve done all four, you can change the wise, or take either a Beginner’s Luck or a skill advancement test related to the wise. If you choose not to change the wise, the wise remains. You don’t lose it in exchange for the test.

Once you’ve used a wise all four ways, choose your perk, reset your marks and try it again. "

Using the character sheet from p. 11, say I used field dressing-wise 4 ways. Now I get a perk, and the perks are “change the wise, or take either a Beginner’s Luck or a skill advancement test related to the wise”. So now my options are
[ul]
[li]Roll (vs what ob?) and Mark a P or F on the Healer skill
[/li][li]Or, I can “change the wise”, does this mean either add an additional wise or i just get to change it to another wise? For example, as a field dressing wise perk, do I drop field dressing wise and add goblin-language-wise? Or if I have less than 4, can I just add the next wise?
[/li][/ul]

I know it’s minor, and I’d prob. let a player gain an additional wise, but maybe that’s just reserved for those long winter nights…also, not sure what roll to make on a skill advancement test.

My reading is that it would be changing it to an entirely new wise. Not a new one.

And no rolling for the test. Just mark a pass or fail, I’d imagine.