Maybe lemon unit. Why don`t you insist Samsung to change 1 unit for you 1 to 1 as it is still before 7 days grace period.

My S10+ took at 6 March 2019 10 AM ++ use until now already 5 days + only charges 3 times.

No doubt if you really set your phone properly the battery can last very long and can cater for full day usage or even more.