I think I understand this more than when I initially read it this morning. I think if you know the context or what happened then you could find an error. If you find an error then you could postmortem it. I think it helps too with knowing how the error happened.
When I’ve done postmortems on my own time it helped to provide the context. It’s hard to describe in words why but I think you can be more specific about an error.
Let’s say you work in a fast food restaurant and you have two orders, and both of them you made the wrong drink. If you find out one order had 4 combos in it and the other was just with some fries then wouldn’t that change things? On one of the orders it sounds like you probably dont know how to keep up with making many drinks. The other error sounds like you’re maybe inexperienced.