Some GMs gave examples that: 80% of the Problems made by 20% of the players. Another example is that the real work may take 1 hour, but it really takes 4 hours to do all the things before and after it. Nick DeVera pointed out another memorable way to think of this is Yak Shaving.
As a tool, its not meant to taken exactly but an abstract measure of by how much may lie beyond my initial assessment.
As a GM ToolStep 1: take a key activity and make an informed guess how much time and resources it would take.
Step 2: multiply all these by 5!
Step 3: rapid fire technique to list out all the possible thing that may need to happen. (this is a Divergent Thinking Technique) and write them down quickly in the small amount of time you have. A creative thinking technique is starting from any point of the alphabet and naming a new thing from any letter up to 3d6 many options. (a creative thinking technique is to push away from old patterns of thinking is by randomizing).
Step 4: Decide how complicated the GM is going to make this, and how appropriate the challenge is to the situation. Use the Pacing Technique (I keep forgetting to cover this) to evaluate time and place (Pacing as a Sensing Technique).
The Players can be involved and practice this technique. It allows them to exercise Divergent Thinking as they rapid fire all the other related options and ideas surrounding their plan of action, as well as other plans of action. If the GM does this he's created an example of a Divergent thinking exercise (from Professor Gerard Poccio's Creative Thinkers Toolkit).
Combined with the Six Hats Technique. this is a Planning session that may count as a adventure session, even though the Players are just planning things out.