Hello Patrick - Thanks for posting to our forums!
When entering customs information, carriers will require actual weights of items. So, the weight (lbs/oz) will need to be entered into the customs form.
However, if you find that the weights from your store are incorrect, you may want to consider setting up your PRODUCTS catalog. This allows you to save accurate weights to your items based on SKU. Then ShippingEasy will map the weights to your shipments and customs forms.
For more information, please take a look at this guide:
If I've misunderstood your question, please clarify for me in the comments below. Thanks!