diff --git a/15.md b/15.md
index bd0f0db8..26015590 100644
--- a/15.md
+++ b/15.md
@@ -95,7 +95,7 @@ Fields that are not self-explanatory:
     "shipping": [
         {
             "id": <String, UUID of the shipping zone. Must match one of the zones defined for the stall>,
-            "cost": <float, base cost for shipping. The currency is defined at the stall level>,
+            "cost": <float, extra cost for shipping. The currency is defined at the stall level>,
         }
     ]
 }
@@ -109,7 +109,7 @@ Fields that are not self-explanatory:
     _Open_: better to move `spec` in the `tags` section of the event?
 
 - `shipping`:
-   - an _optional_ array of costs to be used per shipping zone, only for products that require special shipping costs to be added to the base shipping cost defined in the stall
+   - an _optional_ array of extra costs to be used per shipping zone, only for products that require special shipping costs to be added to the base shipping cost defined in the stall
    - the `id` should match the id of the shipping zone, as defined in the `shipping` field of the stall
    - to calculate the total cost of shipping for an order, the user will choose a shipping option during checkout, and then the client must consider this costs:
      - the `base cost from the stall` for the chosen shipping option