How to set default variant in import file.

-- HikaShop version -- : 6.1.0
-- Joomla version -- : 5.3.3
-- PHP version -- : 8.2.14
-- Browser(s) name and version -- : Firefox
-- Error-message(debug-mod must be tuned on) -- : The default value of one of the characteristics of that product isn't available as a variant. Please check the characteristics and variants of that product

When importing variants via a CSV how do we set the default variant? I'm not seeing a column used to set that value. As a consequence of not having the default variant set in the import, all variants are being set as default and on the frontend we see this message on the product details view:
"The default value of one of the characteristics of that product isn't available as a variant. Please check the characteristics and variants of that product"

When I manually edit the product and set a single default variant and save, then the error on the frontend clears.