Business days include Monday through Friday, but not holidays.
Wednesday, July 4 is a holiday in the US. If you ordered yesterday, Thursday, Friday and Monday would be 3 business days - you'd get it on Monday at the earliest.
Ten business days is two weeks, except for that pesky holiday in there, so if you ordered on Tuesday, July 3, you should receive it on Wednesday, July 18, at the latest.
Most of that time is spent in delivery. Spring and fall are fairly fast. Christmas delivery is slower because of the holiday rush, while July and August are slower because people are on vacation. The 3-10 days is also going to take distance into consideration, but assuming you're neither around the corner, nor all the way across the continent, you should probably expect to see the package about the end of next week.
Cross your thumbs. Sometimes, it gets lost along the way....