I’ve been using Afrezza for six years now, almost exclusively for corrections. Like many others, I observed that Afrezza acted differently than injected insulin. It’s onset, peak and duration all occur sooner than the injected insulin. It’s not important to me why this is the case. It’s only important to me that that is its nature and it is repeatable.
When I account for an Affezza dose, I track it as 50% of its nominal dose. So, when I take a 4 unit Afrezza dose, I find its effect most closely tracks a 2 unit injectable dose. Its onset, peak and duration are all shorter but the cumulative effect approximates about 50% of liquid insulin for me.
A lot has been written about Afrezza on this site. I suggest that you search using Afrezza as the search term and you will find many discussions about this aspect of Afrezza as well as many others.
@Sam19 also uses Tresiba plus Afrezza.