Yeah, the seven business days don't count weekends or holidays. And since this was the week of July 4th, a Federal holiday in the US, a lot of businesses were closed - some for multiple days. Not only is this something that will effect payout processors who are located in US but also any banks. It sucks, but that is not in their control and this will be the same case for almost every single website or clipsite you work for. Business days are only M-F, and holidays don't count for that time. So technically, their statement of the expecting payment on the 11th is EXACTLY 7 business days. But you're right, their website doesn't clarify business days from exact days. Now that I've been in the game for years, I just always assume these sites mean actual business days. It's usually easier that way cuz it's better to plan for later payments and be pleasantly wrong, than plan for earlier payments and get screwed over. Still, they should clarify that a little better on their webpage so everyone knows what to expect. THAT part is definitely in their control!
Also something to plan for in the future: they say they will SEND it within seven business days. But banks can also take several days to process the payment once it reaches them, so it might not be available exactly when they send it. So seven business days can sometimes stretch into eight or even nine before you get access to the money, depending on your bank.
But if we fall in a month with a Federal holiday, you can almost assume that your payment is going to be at least a day or two later than usual.