The new iPadOS can tale up any between 5.5 and 6.0 GBs of free, internal, data storage space.
The amount of available, practical, usable storage is based not only on how much iOS/iPadOS takes up but on the actual size that 1.0 GB is equivalent to, which for Apple 1.0 GB ≈1.075 GBs
Also, iOS/iPadOS devices need to maintain a minimum constant of between 2-4 GBs to ensure nominal, expected performance and function of iOS/iPadOS.
Also, my “current” installation of iPadOS 13.2.3 takes up approx. 5.5 GBs of my iPad's internal storage space.
So,
A 16 GBs storage iPad starts out, after initial drive formatting, at approx. 14.5 GBs of free, internal storage.
After the installation of iPadOS, at nearly 5.5 GBs, leaves 9 GBs of of free, internal data storage space.
iOS/iPadOS needs a minimum of 2-4 GBs of constant remaining storage, AT ALL TIMES to insure/ensure nominal, acceptable operation of all iOS/iPadOS functionalities.
This leaves a 16 GBs iPad with ONLY a practical, usable storage space of between 5 and 7 GBs AND THAT IS IT!
This is virtually NO internal data storage to do much of anything with that iPad!
This is why Apple quietly, silently did away with all 16 GBs iOS device back sometime in 2016.
A 64 GBs storage iPad starts out with 60 GBs, after drive formatting. Minus 5.5 GBs for iPadOS, leaves 54.5 GBs. Minus 2-4 GBs for iOS iPadOS system reserve equals approx. between 50.5-52.5 GBs of usable data storage space.
iOS devices and iOS/iPadOS need to maintain, at the very least, a minimum of between 2-4 GBs of free data storage space, AT ALL TIMES, to insure normal/nominal functionalities/operation and general overall performance of any iOS device running iOS/iPadOS.
Good Luck to You!