Rae from Shopify here. Thanks for posting this question, and welcome to the Community.
Are you hoping to offer free shipping on both products costing $28 and $32, or will free shipping only be an option for customers who spend more than $50?
If you're using shipping profiles, a free shipping rate for orders costing more than $50 can be created by working through these steps. However, if you're using manual price-based shipping rates, then you can offer free shipping on applicable orders by following these steps instead.
Once I have more details about your current shipping set up, and which products you'd like to offer free shipping with, I can certainly help provide more assistance.
Looking forward to hearing back from you!