Dr.PathRoch said:

One practical note: write down what you did and when, before you need it.

I am going to disagree with the direction of travel here. The thread has converged on the tidiest answer rather than the best-supported one, and those are not the same thing.

Reporting back.

Reporting back for the archive rather than for the thread: I did the narrow version of what was suggested, gave it the full interval, and it settled. Posting it because threads without a follow-up are half a thread.

Dr.PathRoch said:

One practical note: write down what you did and when, before you need it.

Saving this. It is the first explanation that did not require me to already understand it.

Adding the clinical framing, because it changes how the question reads. Whatever the answer turns out to be, the method for getting there is the same: state the assumption, do the arithmetic in public, and invite the correction. That is slower than asserting, and it is the only version that survives being wrong.

TrialTracker_MD said:

Whatever the answer turns out to be, the method for getting there is the same: state the assumption, do the arithmetic in public, and invite the…

This is my experience too, for whatever a second data point is worth.