Option 1:
See Structure flat webhook request to be able to iterate over it - #5 by samliew
You can do that by setting the Webhook “JSON Pass-through” to YES (it is “No” by default), when creating or editing a webhook.
Then, you will be able to map the entire JSON body payload in another module, which would allow you to dynamically extract the number of items.
Option 2:
You can use a repeater module with ProdTotalLines, and use the map
function to extract each of the five keys associated with the product.