Whatever you do, DON'T look at one of those tables which shows your raw marks compared with your aligned ones. It will make you depressed.
That being said, ancient requires a lot less constant study than Chemistry, imo, and the scaling reflects that. There's also the matter of your peerage and how well your class will perform, and where you are in that class, marks-wise.
With ancient, it's really difficult to say what kind of affect your marks will have on your UAI- I was in the top 2 or 3 people in my year, my year did very well, and I did very well in the exams. Hence, my marks weren't slaughtered.
It's important to remember that scalling is a moot-investigation, meaning that 1. you can't do anything about it, 2. it will make you unhappy if you compare your scalling with other subjects, 3. you don't know exactly how well you will go in external exams, and 4. you won't know how well your other peer group does in exams.
Try not to worry about it too much, and remember that if your the (for example) 5/40 people in your grade, and your grade does well, you won't be too disadvantaged.