Question about “older than” date when deleting messages

My site uses the Better Messages plugin to organise messages in “threads”.

What happens if I set the “older than” date for deleting messages and it falls in the middle of a thread?

Example: I set the “older than” date as 1 Jan 2024.

A thread has it’s original (starting message) sent on 1 Jan 2023 and the thread continues up to Dec 2024.

What happens?

A. The entire thread gets deleted.

B. Only messages older than 1 Jan 2024 get deleted, the rest of the messages in the thread remain intact.

Thanks.