I did this test about 3 weeks ago.
It contains a mixture of:
- basic algebra maths (SHL style questions with graphs and lots of basic computations)
- Data sufficiency maths (GMAT style - i.e. inferring results with key pieces of information)
- Error spotting (literally spotting a missing letter or digit in lines of code)
There is a practice test on the testing platform with pretty similar questions which you can take as many times until you get it all right, so I'd just advise to use this as the source of practice, as the test contains elements of all the different types of common maths tests.
In terms of difficulty - time was relatively pressured; questions start easier and get fairly tricky at the end - I found it harder than BCG and Bain maths tests, but by no means impossible.
Hope this helps - good luck!