4 A levels for maths

Hello, I am applying to Cambridge this year for maths. Currently I am doing 4 A levels: Maths, FM, Physics and Computer Science. As the deadline approaches for the UCAS applications, I need to make a choice as to whether I apply with three A levels (M, FM, Phys), or do all 4. I am aware that Cambridge does not really care about it, but I also heard from an admissions tutor in Churchill FM might not viewed in the light of a "Full" A level given one must do well in Maths to do FM. But my school has also advised me to drop one, and I have reason to believe them as they are historically very strong with getting people in (I think 11 people from about 25 ish who were interviewed got offers one year, despite being a state school), where the average student does 3. Due to this conflicting information, I am unsure what to do. I am good at STEP and I will in most likelihood meet the requirements either way, but right now my only priority is getting in, so I need to make the best choice for that, does anybody know if the FM thing I noted applies for the mathematical tripos, or if I have taken it from the wrong context? If it helps my predicted grades are A*A*A*A (The A is CS)