"Limbo is... well, shorter to say than 'interdimensional space,' for one thing. He was doing teleportation research for his master's thesis, and - you could argue that it worked, but he missed the instructions for getting out of the space he got into again. Wasn't much to see - I'd wonder how he was still save afterward except I don't know how aware he was that time was passing. He was fourteen years older than me when he got stuck and now he's two years older than me."
She's just counting her blessings that she got him out before she was the older sibling. It's been weird enough as it is.