So you always only need to type using the two rows at the top, maximizing the space and allowing for big large letters. The hidden letters are accessible through the alt key, alongside symbols and numbers.
This policy exists to inform you that the keyboard does not record, save, harvest or send any data of any type. The application, and its keyboard extension is self contained and does not keep any data. The active source code is also available to demonstrate that the keyboard does not hold onto your content.