Yeah, I can see why that would be confusing. I still think it's just a base 5Mpbs for everything.

Some more verbiage from their website:

We're built for life on the go, so instead of giving you extra speed you don't need (and making you pay for it), you get unlimited data at a speed that's perfect for streaming.

We’re built for life on the go, so instead of giving you extra speed you don’t need (and making you pay for it), you get unlimited data at speeds up to 5 Mbps. That means video will typically stream at a resolution of 480p, nice and crisp on your phone. Here are some more details about what 5Mbps will mean for you:• Streaming Video: 1-3Mbps• Video Chatting: 1-2 Mbps• Scrolling through your social feeds: 1 Mbps• Streaming Audio: 0.5 Mbps