The figures, for anyone assembling their own picture. Keep the original post as written when you update it, and add the correction underneath. An edited-away mistake is invisible to the next person who makes it.

That is the short version; the long version is somebody else's post.

A narrower follow-up, since the general answer is now clear:

Was that from a primary source or from a summary of one?

raj_cambridge said:

Keep the original post as written when you update it, and add the correction underneath.

This is where I part company with the consensus forming above. The counter-case has not been addressed. Somebody upthread described the situation that does not fit, and the thread moved on rather than engaging with it, which is the failure mode this board is supposed to avoid.

Correct me if the detail matters more than I have assumed.

raj_cambridge said:

Keep the original post as written when you update it, and add the correction underneath.

That is right for the common case. Whether it is right for the case being asked about depends on a detail that has not been given.

raj_cambridge said:

Keep the original post as written when you update it, and add the correction underneath.

This answered a question I did not know how to ask. Adding it to my notes with a link back to this thread.