I can’t think of any, but mental arithmetic can be hard sometimes (and I’m being honest there, mine is ****ed from decades of either using a calculator at school & Excel at work).
A visual indicator for your change is always better then none. Sometimes I change stuff arround and I’m so sure I thought of everything but my dmg is lower in the end because I missread something or overlooked another thing untill I#m realy awake again ^^.
Sure in the end it’s most likely a user error but then again visualisation will help a big deal.