Is this the store name (username under admin)?
No, its the filename of the xml that you are sending to Google.

You should register a test feed at google to upload multiple times while you sort out the errors in the your feed.
Call it test in the admin and it will be created as test_products.xml
Register it as test_products.xml.

Then when it is uploading 100% and Google has stopped complaining about the data or formatting errors, register a new feed eg: YOURSHOPNAME_products.xml
Change the name according in the admin and upload, then wait for Google to verify it....