I have a felling the software for your keyboard is opening the calculator and Windows is also invoking the opening of calculator as well. Take a dive in the keyboard software and see if you can possibly unassign the button or something to the effect of stopping the keyboard software from opening it.
On the other hand, this may be a double edged sword where if the keyboard software is set to not allow the calculator to open, the button may never open the calculator. Now if you don't use the keyboard software, the calculator button will get invoked by Windows and only Windows and thereby just one instance of the calculator will open.
If you're not using the keyboard software for fancy stuff, then just uninstall it.
You said it's an AZIO keyboard, but what model? I don't even think you have keyboard software installed which throws out my theory for some other software being invoked by the press of the calculator button.
If you are positive there is no keyboard software, and tell me the model of keyboard and I verify that to be true, run Autoruns, go to File and save the ARN file. Zip the ARN file and upload here. This way I can have a peak at anything that
might be invoking the calculator as well as Windows.
Autoruns for Windows - Windows Sysinternals | Microsoft Docs