So you already know that it means an extra teat on each side of her udder. Boers are allowed to have extra teats. In a dairy goat, it is a fatal flaw and should always be culled out of a herd and the does or bucks with the trait not bred. Boer goats are meat goats, so they can get away with having extra teats. It is allowed in their standard, but breeders SHOULD work towards normal teats.
The extra teats are not always functional, as indicated, meaning milk does not come out of them. Remember that goats only have two milking portions of their udder, unlike a cow that has four. Extra teats do not mean extra milk production, just a new outlet for the milk to flow (sometimes).
So she'll have extra teats, but possibly no milk flow from the extras This can actually cause kids to starve. Why? They'll attempt to nurse from a teat that does not function. If you aren't on top of it, making sure they learn to nurse from the functional teats, you'll need to bottle feed them so they do not die. You can hope they nurse from the correct teat, but you will need to keep an eye on them and make sure they are.