Hey Mike!
Thanks for sharing that screenshot, it looks like we got part of the name but are missing the rest of the name and then it will work as intended!
In the output, it has @TTAX:=... we need to expand the ... to reveal the full name.
If you can share that screenshot we can get the full name, and add it into the console log so it will read console.log(TaxFillTableInv.data['@TTax:=fullName'])
The other way we can view this is in the query's state tab after you run it. Inside of the query's data field we can see the full column names which will show us '@TTax:=fullName' so we can add in the correct name to the console log.
My colleague Paulo shared a link with me to another post where he shows how to view a query's state. Check out his post and the screen shot here if you are unable to expand the output to see the full TTax column name.
Hope this helps and let me know if you have any further questions! 