Pen mechanics when the cartridge is nearly empty — does this still hold?

Asking directly, because I could not find a straight answer: Pen mechanics when the cartridge is nearly empty — does this still hold?

Practical question with the units stated, because I have seen how quickly these go wrong without them.

I have a 15 mg vial of tirzepatide and I am working to a 5.0 mg step. My syringes are U-100 insulin syringes, 0.3 mL barrel.

I can do the arithmetic and I have done it twice, getting the same answer both times, but I would like someone to check the reasoning rather than the number — specifically whether I have thought about the residual volume correctly, and whether the graduation I am landing on is one a person can actually read.

Picking up post #2: that is the part I would want checked first.

Dose counters: pens show the remaining number of doses. When the counter reaches zero, the pen is empty and cannot deliver more. Noting the counter before injection prevents running out unexpectedly.

I disagree with the reply above, and I think the disagreement is substantive rather than terminological.

The distinction being drawn does not survive when you look at the published data for this specific question. I would be glad to be shown wrong on this, because the version I am arguing against is more convenient.

Picking up post #20: that is the part I would want checked first.

Dose counters: pens show the remaining number of doses. When the counter reaches zero, the pen is empty and cannot deliver more. Noting the counter before injection prevents running out unexpectedly.

On post #26 — agreed on the reasoning, with one qualification.

Pen mechanics: most pens are dial-and-inject devices where you dial the dose on the pen and push the button to inject. Understanding your specific pen's mechanism prevents dose errors.

Storage after first use: most pens can be stored at room temperature after first use, even if unrefrigerated, for a limited time (often 28 days). Check your specific pen's labelling.

post #42 answers the question as asked. The question underneath it is different.

For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use.