Note - Keep fields blank if you don't want to change.

Type  -> Type of the variant (must be packet / loose case sensitive).
Measurement  -> Measurement of the variant.
Measurement Unit ID  - > Measurement Unit ID of the variant (You can find Measurement Unit ID in settings > units section).
Price ->  Price of the variant. (Must be greater than discounted price).
Discounted Price  -> Discounted Price of the variant 0 if no discount. (Must be less than price).
Serve For  -> Availability of the variant (Must be Sold Out / Available case sensitive).
stock  -> Stock available.
Stock Unit ID  -> Stock Unit ID of the product variant (You can find Stock Unit ID in settings > units section).
Product ID  -> Product ID of the variant (You can find it in products table).