CVar displayFreeBagSlots

Whether or not the backpack button should indicate how many inventory slots you've got free.

Default Setting

 * 1

Possible Settings

 * 0:Off
 * 1:On

Changing this setting
In-game, type the following /console displayFreeBagSlots setting

Alternatively, you can exit wow, open the Config-cache.wtf file, and add the following line: SET displayFreeBagSlots setting