How do I use tinydb to fetch value in order to make a calculation?

Hellò! New to AI2 me too .
Is it possible using TinyDB how calculator storage ?
Is it possible to see an example?
I need of data calculator storage visible in multiscreen (example: 100 in storage how result of 400 - 300).
Thanks in advance for any help

Most people building calculators don't need more than one screen or TinyDB.

What is so special about your calculator?

I'd like to build a sort of diary with calculator ..

Those are typically spreadsheets.