I would say it will definitely significantly worsen your chances!
The first 7 sections are bookwork. There is almost always a question asking for something on this in the exam, worth in the region of 5 marks. However, if you wish to take the risk, sections 2-5 come up most often, and are therefore the more important to learn.
Section 8 is on single figure indices. It is a numerical section, but is unlike any other of the numerical calculations you do elsewhere in the course. However, the good news is that it is really easy, you should be able to get to grips with it in a day, possibly half a day, and just requires you to learn and apply 4 formulae. And (in addition to the 5 marks for the bookwork), this comes up in nearly every exam, and has been worth up to 9 marks in recent papers (though sometimes as few as 3).
The thing is, there are few relatively "easy rides" in CT5, but this is one of them, and you really don't want to miss it.
Good luck
Robert
