Eating Egg Matzo Has Rules?

On the box of Manischewitz Egg Matzos is says this:

According to Ashkenazic practice, all egg matzo may be eaten only by the young, infirm, or aged. If you are of Sephardic ancestry, consult your rabbi.

Challah is taken.

Oops.

I already ate it, don't have a rabbi, and am not exactly what you'd call young, but I'm not aged and infirm either.

Maybe I should switch to the unsalted?

Oy vey!

And can anyone explain to me what "Challah is taken" means?