hans_munich said:

Almost every unanswerable question in these threads is unanswerable because three things changed in the same fortnight, and no amount of subsequent…

Right, and the exception is worth naming rather than left implied, because the exception is where people get into trouble.

pam_stl said:

Correct, and worth adding that it is reversible.

Genuinely useful, thank you. I had the facts and not the framework. Taking it to my next appointment.

hans_munich said:

Almost every unanswerable question in these threads is unanswerable because three things changed in the same fortnight, and no amount of subsequent…

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.

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

Adding the numbers, since they settle part of this. 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.

Moderator note: the sourcing question belongs in the vendor section and has been split out. Carry on.