Is it normal for the new battery of iphone to drop 9% in four days?

Hello, the battery health of Apple mobile phone dropped by 9% in four days. I don't think this is normal. I think your mobile phone is useless. If the battery is less than 20%, it can't be used any more. But to charge the phone in time. In addition, you can't play with your mobile phone while charging, which reduces battery loss.