Why does the battery show not fully charged in Coconut battery?

When this iPad is fully charged both Coconut Battery and iMazing show 90% for state of charge. I left the iPad plugged in to see if the software would report 100% after some time, but there is always this 10% discrepancy between the device and the software. It makes me wonder if the design capacity is correct as well at 77%.

My other devices all show the same charge percentage as the software does.