Wheel measurement help

Wheel measurement help needed - - Made the mistake of buying wheels online from the wrong company. Filled out their shop by car and make tool. Come to find out - according to manufacturer, Voxx; those wheels should never have been offered for my car. Wheel hub too small for the car. Sent pics and was told the rust dust seen on the hub was stopping the fit. I provided the dimensions and explained there is not 4 mm of dust. Then they said nothing they can do. $1700 lesson.

Online seller refused to take them back as I missed their 30 day fitment window. They do not even know the size they sent.

I know the bolt pattern and measured the hub bore. Is there a way I can measure the offset myself? Thanks