The name of the subscription tier is “Disney+ Standard with Ads”. So what is says is “Subscribe and get 7 days of [subscription] on us”. “On us” in English slang means “we pay for it”. So what the sentence means is “You will get to use a service called ‘Disney+ Standard with Ads’ for free for 7 days”
But yeah this is total word salad. It’s like they’re deliberately trying to weed out people with common sense and critical thinking abilities.