Only for a little bit with 〜だけ

Grammar Explanation: Limiting with 〜だけ

While waiting for his brother, Akatsuki finds Akari. He decides to pass the time by having Akari give him a tour of the area, but she explains that as a trainee she can’t take on customers by herself. Akatsuki hops into Akari’s gondola, saying it’s okay as long as he’s not a customer; he’s a friend.

灯里(あかり):: 「本当(ほんとう)にちょっとだけですよー」; “It's really just a little bit!”; Literal: “It really is only a little.”

Akari is limiting the the gondola tour to 「ちょっと」, a little bit.

Key Points

1だけ limits the amount

だけ marks a limit, so Akari means “only” or “just” this much.
Here it narrows the gondola ride to a very small amount of time.

2ちょっとだけ is a common set phrase

ちょっとだけ means “just a little bit” and is very common in everyday speech.
Akari is reassuring him that the favor will be brief.

3Sentence-final よ adds emphasis

The よー ending makes the reassurance sound emphatic.
It is not new information so much as an insistence on the limit she is setting.

Vocabulary

本当 (Truth)

本当(ほんとう) means truth, reality, or really. The nuance is that something hits what is genuinely the case.