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.
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.