When the calculator loads, the From Value will be copied from the x register.
When you return to your Focused or Formula Calculator, the last "To Value" will be in the x register. Access this value using the RCL-last x.
Available only in the customizable version of CALC 1
Tapping the "Create Key" button will create a key and copy it to the clipboard. You can then paste the key on a calculator. See Copy and Paste keys for more information.