Gradebook

I don't fully understand the point of having the course total have an option for maximum points when using the weighted mean of grades aggregation type. It seems to me that this shouldn't even be an option and it should simply be calculated. It has proven to be a problem because if it changes or accidentally gets adjusted it can throw off the gradebook even though it should have no bearing on the grades due to its calculated nature. What am I missing? Why is this even an option? Is the final score simple scaled to match whatever number is placed there? Is it to provide a greater range of accuracy? Any clarification on why it's there and how it's used would be great. Thanks.