Hi wilmamae,
Thanks for posting your question here. When you list through Auctiva, as on eBay, there is only one Value field that can be filled in for each Custom Item Specific detail that you create. However, you are able to add multiple custom details within the Custom Item Specifics section of each listing.
I believe the best way to go about this would be to create a separate Detail Name in the Custom Item Specific section for each different measurement you wish to enter in your listings.
I hope this helps. If you need any further assistance with your account, please feel free to contact our customer support team by mousing over the "Help" tab on our site and selecting the "File Support Case" option.
-Mike