PRODUCT OPTIONS - "CODE" in variable lists? infusionsoft/ultracart

trying to get infusionsoft and ultracart to communicate effectively since there is an error in our logs of the data showing an error when it comes down to “product mapping” and something with “integers” HELP! For each product we have on our STOREFRONT/MAIN STORE/MAIN WEBSITE on ULTRACART, we have 5 products. Each one has their own parent sku number, but then people must select “one time purchase”, “ships every 2 weeks” “ships every 28 days” . (all the prices are the product are the same for each shipping option FYI.) So in the “frequency” list I created under PRODUCT OPTIONS in manage infusionsoft product, I put the name of it “One Time Purchase” and in CODE section I put the unique SKU number from ULTRACART that is tied to that one time purchase specific item, and did so with the SKUS from the other shipping options and put them in the CODE section of the list on product options on infusionsoft. but on the main page of manage products, it asks for the “SKU” and I have a feeling im not doing the list right or using that “code” section right, otherwise product mapping wouldnt be getting errors. Not Sure if I need to put all 15 some off items as the ACTUAL products in infusionsoft and not use the lists…