Low iPad battery even though it's almost fully charged?

Hello Hello,

I wanted to ask if anyone knows what it means when the battery indicator on my iPad suddenly turns red and shows very little charge? I mean, the internet symbol isn't even displayed, and the percentage isn't even shown. However, it can't be because I don't have a battery, because I had over 70% one time. It's happened twice already, and after a restart it was back to normal.

Thank you for any answers!💟