Thirty nine buttons

[explorationist]

[The girl subtracts twenty-nine and four in the corner of the journal because she has nothing better to do than sit around and wait for something interesting to happen. Unless the castle really liked seeing her miserable, there was no other reason she could think of to why it would keep her here for a whole almost-year. Sighing, Coraline begins to sketch something that looks a little like this into the journal beside the numbers]

How long do kids usually stay here?