Creating A Valid CSV File

I’m using a Mac with Numbers (Spreadsheet)

I can download a Template file into Numbers and populate it with product data.
Then Export to a CSV file.
If I look at the CSV file it appears fine to me - data is there INCLUDING the top 3 lines that are required by Amazon
But when I ask to validate the file - it errors on top 3 lines being invalid.

Does anyone know if this is a Mac/Numbers issue?
or am I doing something untoward (again!)