Delete individual mail from a conversation using filter gmail

I have created a filter to label all the OTPs that come to my mail but there are thousands of them which I want to delete.

I have tried deleting using older_than:2d label:OTPs -label:GST but I want to reduce that manual effort. I want to know how to delete individual emails from a conversation under the label OTP which are older than 2 days by creating a filter.

From a conversation of 21 mails, only 7 are such that needs to be deleted.

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