Folder size calculation normally only happens when you explicitly request it (e.g. via Edit > Calculate Folder Sizes, or by hovering the mouse over a folder if the tooltip is configured to show the folder's size).
It can be set to happen automatically (see the Folder size claculation FAQ) but you wouldn't normally want that as it causes lots of extra disk access for information that is usually not wanted.
As for the label, if you show us how you have configured things we might be able to see what's wrong.