There are no set topics, but here is an indicative list:
Algebra (+Binomial Theorem)
Those should be covered by 5th year as they are the basics and other topics build up on them. Some people would have the whole course done in 5th year, but others would have less than this.
Good grip on Algebra and Trig covers at least 3x50 = 150 marks
Lines/Circles/bit of Geometry should cover at least 1.5 x 50 = 75
225/400 is like 60 + 25 bonus will bring you to 85 Points which is good in my opinion.