I don't understand how a bubble chart based on percentage of the total from various departments fixes receipts? Knowing the percentage of my total that comes fr

I don't understand how a bubble chart based on percentage of the total from various departments fixes receipts? Knowing the percentage of my total that comes from a specific department isn't a problem I have, though maybe it is for others. I'd be more interested in being able to self categorize my purchases and breaking down the percentage that way.