Error? Or something else?

[RaVii]

I encountered a strange problem today while using my phone. His battery was at 67% and then after a while the battery dropped to 2%, After restarting, the battery was back to 67% , What's the problem? The phone or the program? I don't know and I'm asking for some help 

[Koudmaker]

First time hearing that but maybe a software bug or a battery voltage problem. But wait and see if it will happen again.

[RaVii]

I doubt it's a battery problem because when I took my phone to the service center in April, they didn't find anything. 

[Mattias_ASUS]

Hello @RaVii 

This is the first time I've heard of this too, but it's very likely it was just an UI bug. 
Please let me know if this happens again.

[RaVii]

This is the first time I've encountered this,But I will keep you updated if it happens again.