Yo BlueGas! I just got an email about the MRS thing too. From what I've heard it, it's like a test that basically tests your maths abilities and stuff, and you have to book a session for it. I'm not sure if that's exactly what it is but my friend told me that so idk. It's compulsory and you'll need to do the two practice things on the website. I booked for it just now.
However, it's only for enrolling engineering and science students.