WB Eyedropper brightness value

Hi everyone,

I'm using both Lightroom for Android and desktop version for retouching photos quickly.

When touching white-balance in desktop version, I usually use eyedropper to pick a neutral gray pixel to get the most accurate color. However, I find it quite difficult to do the same thing on Android version as there's no brightness value shown with the picker (I can't determine if it's truly balanced or not).

Do you have any suggestion? Thank you so much.