I did it exactly per trailhead but get this error:
"Challenge Not yet complete... here's what's wrong:  Please check that your report includes at least all of these columns: 'Supply: Supply Name', 'Unit Cost', 'Quantity' and 'Total Cost'."
I do have these fields perfecty correct, then why this error?  I have recreated the report and dashboard 5 times, but still the same error!

I keep receiving the following error message: 
Challenge Not yet complete... here's what's wrong: 
Please check that your report includes at least all of these columns: Supply: Supply Name, Unit Cost, Quantity and Total Cost.

But, this is exactly what my report displays:

The Error I get is: "Step Not yet complete... here's what's wrong: 
Please check that your report includes at least all of these columns: Supply: Supply Name, Unit Cost, Quantity and Total. 
Note: you may run into errors if you've skipped previous steps."
this is my report:

not sure where I made a mistake