We recommend selecting one variation to run a launch for when you have a listing with multiple variations.
The best way to go about this is to ensure that the URL and ASIN link to the specific variation you intend to launch. You will also what to clarify which variation the coupons apply to through the title that you create for your product on the Viral Launch Launchpad. (i.e. 'Small Black Slippers' or '30ct multivitamin')