Our “free shipping calculator” in Shopping cart widget is just a front-end layout to show up. Shipping rate and order value come from Shopify data (back-end) not our site, so we can not interfere to Shopify data and get them to build our “Free shipping Shipping Threshold".
In that case, please follow these steps:
Step 1: Go to Shopify Admin> Setting
Step 2: Set up minimum order price
Step 3: Go to Customize to edit Our “free shipping calculator” same to the Setting above
Thank for reading!