Hello @Mark_Anthony_Ching, this is definitely where customizing the narratives can be a bit tricky. It may take some time playing around with adding different calculated fields and managing the calculations available in the insight.
Here is a link to a community question that I worked on which may give you some insight on how to get closer to your solution. I think utilizing the IF statement with the TotalAggregate inside the FOR loop is going to cause some problems though. This may be a scenario where you will want to manage the IF statement in a calculated field, import that into the Insight and then try adding Quantity as a totalAggregate. That might be the best course of action.