Assuming you're an American candidate, it's probably between 2 and 5 PM where you are right now. That means you still have time to get a lot of studying in tonight and my advice to you is to take advantage of every minute. Let's say you usually go to bed at 11pm – you have 6-9 hours to study still tonight. For BEC, that should get you through at least a couple chapters if not more.
Think of all your time like that – how much you can use for studying. That's what it will take to be ready for BEC by 8/28.
How much time can you study through the week? Let's say, theoretically, you think you can get 2 hours of study per week day. (A lot of people who work full-time do more than that, but each person's abilities vary, so we'll use 2 hours for an example.) There's 18 business days before your exam, so that's 36 hours of studying at 2 hours per work day. On the weekend, let's say you can get in 14 hours (2 7-hour days, 1 10-hour and 1 4-hour, etc.). There's 3 full weekends between now and then, so that's another 42 hours. That gets you up to 78 hours plus whatever time you can still study today – I've seen a lot of people say around 80 hours is about right for BEC with a lecture-based course, so you should be in good shape.
That's the way you have to think to make your deadline – look at each day and each minute and make the most out of it. If the weekends seem like 14 hours would be too much, do more during the week, etc.
This is all assuming you're doing lecture-based study. If you're doing book-based, then you probably won't even need that much time. I did book-based and would have to look back to remember exactly how much study time I had, but know it was below 50 hours, want to say more like 40 hours, so if you're book-based, you should have plenty of time.
Either way, just put your nose to the grindstone and get to work! 🙂