I agree an interesting question, the rules say you should have withdrawn the excess contribution less the allocated loss. thus had you withdrawn cash you would have something less than the $6K so perhaps the proper tax basis is the FMV on date removed and the loss stays in the Roth. Here's from another thread
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If you withdrew your 2022 excess contribution to your Roth IRA before the due date of the 2022 tax return (April 18, 2023), make sure that you also withdraw the related earnings/losses. You have already done this.
On your 2022 tax return, you do not report the excess contribution as it has been withdrawn. The earnings have to reported and taxed in 2022. These earnings are also subject to 10% early withdrawal penalty if you are younger than 59 1/2.
If there is a loss, that loss is not deductible.
