Moving Assigned Monies Between Categories

Question: Sometimes, when moving money from one category to another, does the losing category change to $0.00, while other times, it will throw a -(minus) in front of the moved amount?

For example, sometimes, when moving $50.00 from groceries to insurance. Groceries "assigned" changes to 0.00, while other times the groceries will change to -$50.00

My hunch is it's got something to do with whether the $50 assigned to groceries was assigned in a previous month or if it was assigned during the current month.

I was playing with it and changed the -$50 to a 0.00. What I found was that it removes $50 from "ready to assign" and reassigns groceries $50

Thanks in advance