Sadly no actual mathematical representation. Look at "991EX" as an example. Units are very cumbersome to carry around in a calculator when you usually know anyway which it is or has to be.
The biggest problem over found with this is how unexpectedly easy it opens up the Android keyboard and obscures the keypad, but this is otherwise a fantastic tool. I've been searching for a no-Enter FOSS algebra calculator for literally years!
This looks like an awesome tool for anyone who loves having a powerful calculator at their fingertips! The calculate-as-you-type mode is perfect for quickly solving problems without losing your train of thought. Plus, those screenshots make it look super clean and easy to use.