I'm running the latest version of woocommerce & WP.
After I setup a product and save the attributes as a variation.
I can see in the variable tab where it says no default defined.
If I click on any of the items of the dropdown and add or expand all towards the top it doesn't actually do anything.
I'm under the assumption this isn't the normal behavior.
I don't have prices set for the item (i don't see an option to do so for the variations) because nothing aside from the basic dropdown that says no default defined loads.