Meaning of じゃないんじゃない?


I recently came across the phrase `じゃないんじゃない` in this sentence:

> Clerk: 「でも うちで売{う}ってるアイスじゃないんじゃないかしら。」

For context, some kids are claiming they have a winning popsicle stick but the
clerk can't seem to recognize it.

Here, I believe the clerk is saying `But I don't think we sell this kind of
ice cream here`.

However, the `じゃないんじゃない` is throwing me off because it looks like it's
negating the sentence while also asking for confirmation, as if the clerk
doesn't believe her own words or something.

How should `じゃないんじゃない` be translated here?




> でも うちで売ってるアイスじゃないん **じゃないかしら**

「～じゃないかしら。」「～じゃないかな。」 can mean "I suspect..." "I think..." "Isn't it...?"

うちで売ってるアイス means "ice cream that's sold in our shop". (うちで売ってる is a relative
clause that modifies アイス.)

So the sentence basically means...

> "But, it is not the ice cream that we sell, is it?"  
>  "But, I think it is not the ice cream that we sell."




> でも うちで売ってるアイスじゃないん **じゃないかしら**

「～じゃないかしら。」「～じゃないかな。」 can mean "I suspect..." "I think..." "Isn't it...?"

うちで売ってるアイス means "ice cream that's sold in our shop". (うちで売ってる is a relative
clause that modifies アイス.)

So the sentence basically means...

> "But, it is not the ice cream that we sell, is it?"  
>  "But, I think it is not the ice cream that we sell."

