Full iPad memory.

Perhaps this may help: https://support.apple.com/en-us/HT201656

A16 GBs iPad is NOT too useful in 2020!

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=1.074/1.075 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 installation of iPadOS 13, currently, takes up 5.2 GBs of my storage

So,

A 16 GBs storage iPad starts out, after initial drive formatting, at between 14.5-14.8 GBs of free, internal storage.

After the installation of iPadOS, at say 5 GBs, leaves 9.5-9.8 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.

Compared this to a 32 GBs internal storage iPad.

A 32 GBs storage iPad starts out with nearly 30 GBs. Minus 5.0 GBs for iOS leaves approx. 25 GBs. Minus 2-4 GBs for iOS iPadOS system reserve equals between 21-23 GBs of usable data storage space.

This is between 3-4 times more usable, practical internal data storage of a 16 GBs model iPad!

If you need to free up free data storage space on an iPad/iDevice, you need to start by backing up your iPad to either Apple's iCloud or by connecting your iDevice to a computer running the latest iTunes and/or some other offsite, “cloud” data storage/backup services, like Google Drive/Photos, DropBox, BOX, Amazon Cloud Drive, Flickr ( for photos/images ), etc.

Then, delete any installed apps that you no longer use or use infrequently enough that they aren't missed (you can always reinstalled any purchased or free apps at some time later, as you need them).

Then, thin out/delete any music/videos/movies/TV shows/podcasts/screen recordings/images/eBooks/

eMagazine/iBooks/audio books/Documents/PDFs, etc.

If you use a POP email account on your iPad, delete/thin out any old saved emails that maybe saved to your iPad.

To permanently delete photos/images off of your iDevice go into the Photos app and find the Recently Deleted folder/album and permanently delete any photos/images stored in that folder/album.

Also, you can check to see what other stuff is eating up all your valuable data storage space by going into the Settings App,,General Settings Panel, in the right hand column, tap Storage & iCloud usage panel ( in iOS 11, it’s iPad Storage ), in the top Storage Panel, tap the Manage Storage panel, wait for a list of apps to generate that will tell you how much space each app is taking up on your iDevice.

Then, do a hard reset of your iPad by holding down both the Home and sleep/wake buttons simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons.

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!