One is correct according to the book.
https://www.dndbeyond.com/sources/dnd/tcmp1/backgrounds#Amnesiac

I’ll let the devs know the listing text needs corrected.

I was told that’s working as intended because of this passage in the background’s description:

You don’t choose skill proficiencies or a tool proficiency when you select this background, and you don’t determine the two languages that are part of your origin—these are parts of your past that you are missing. Instead, you can pick one of those proficiencies or the languages during play at any time.

That’s my understanding, yeah. Or at least you wouldn’t choose them at the start. It sounds like the intent is for you to “discover” the languages you know during play.

For example, maybe you’re exploring a cave and find a wall scrawled with Abyssal, and your character suddenly realizes they can read it. Maybe they know why as some forgotten memory clicks into place. Maybe it’s still a mystery, another clue to a past that remains unknown. It’s up to you. You can make the choice at any time, and then it’s locked in for the rest of the game.