From AT&T’s website:

Data from your mobile hotspot data Add-On is used before the hotspot data included in your plan. This Add-on allows you to connect compatible devices to the internet using your phone. It is recommended that you use all or most of the hotspot data in your plan before buying a mobile hotspot Add-On.AT&T broadband info is available at [att.com/broadbandinfo](http://att.com/broadbandinfo) .