In my case, %ISE_EIFFEL%\ is:
C:\Program Files\Eiffel Software\EiffelStudio 24.05 Standard

Copied calculator directory to C:\dev\eiffel\calculator
Open calculator.ecf

Target Selection:
Choose one target among:
classic
dotnet
Selected dotnet, then clicked: "Select target" button.

Choose Your Directory
Location:  C:\dev\eiffel\calculator
[x] Compile project
Click: OK

Eiffel Compilation Succeeded
F5 to run.
EiffelStudio Warning
An error occurred during initialization of the ICorDebug Debugger or during the Process creation (.NET).

calculator.zip is downloadable from
    https://www.adrive.com/public/AdKt3j/calculator.zip
This includes the entire EIFGENs directory.

Is there anything else you need?