Thank you for posting to our forums!
Looking at your Shipment History, I see you have a mix of First Class and Priority Mail shipments. For the First Class shipments, you would not see a difference but for the Priority Mail shipments, you would see a difference.
Those on the free Starter plan receive Commercial Base Pricing (CBP) on all USPS services. And those on a paid subscription (Basic or above) receive Commercial Base Pricing(CBP) on First Class Domestic and Commercial Plus Pricing (CPP) on International and Expedited (including Priority Mail).
You can see our rate tables linked here: ShippingEasy's USPS Rate tables
You can also view what is included in each plan type here: What is included in my plan?
I hope that helps!