Deciding how long it will take

Question regarding Monday Hour One.
We get to decide how long a task will take.
How about I have to edit some videos for an online course. The video is 20 minutes long. There is no way I could edit this video in 5 minutes, right? I need at least enough time to watch the whole thing (since I left some blanks here and there in the video that I know need to be cut out). Or I could decide not to edit it at all so it would take 0 minute to edit, but then it would be D work (far from a B-). Does that mean if I choose to get it done in 5 minutes, I need to outsource the editing? I guess that would work…
I’d like additional insights from a coach on this.