Disable Messages in iCloud on my iPad to free up storage

I set up my iPad (Gen 8 running 18.1.1) and an hour or two later received an alert that my iPad storage was full. I noticed that Messages were taking up 12.75GB of my 32GB of storage. I don't want or need messages on my iPad as I can access Messages on my iPhone, laptop and Mac. I went to turn off messages in iCloud on my iPad. After bit of watching the wheel of death swirl around, a message appeared "Messages in iCloud Messages have not been fully downloaded to this iPad". Then I had a choice to click Disable and Download or click Cancel. If I click the Disable and Download, what data is going to be downloaded where??? My iPad storage is full at 31.74GB out of 32GB. Where could any more data be downloaded or stored on my iPad? How does that work?

Would some brilliant mind out there please explain?