My 2017 iPad came with 83%. I am not sure whether it is recommended to fully charge a device you dont know how long it will be in a shelf. I am sure Apple charges their iPads to around 85% before they get boxed as you shouldnt fully charge lithium ions battery if it is not going to be used for an undetermined period of time.
Regarding battery, I am absolutely amazed by this iPad. I've been getting 14 to 15 hours usage time!