The Weak aura is designed to glow with an icon and a timer when you have 3 stacks of the buff that grants you an instant Enveloping mists cast. Only triggers when Chi-Ji is active and you are in combat by default.
Intended to be used with the addon OmniCC for cooldown and duration tracking numbers as in screenshot 1 , otherwise refer to screenshot 2.
If you are not using OmniCC, go to " Display " setting and at the bottom click on Add Text and make sure the field " Display text " is showing " %p ". That will make the remaining duration of the buff show up on the WA.