In the case of variation product while uploading on jet you need to map jet attribute, for mapping attribute, there are very simple steps
Go to product section
Under product section, there is map jet attribute option
click on map jet attribute, from there you can select the attributes which you want to keep for your variant products
You can take help of given link-
https://shopify.cedcommerce.com/jet/how-to-sell-on-jet-com#sec1-6