Hey Vani.

Along with the time you devote for CLAT, efficiency is also required to prepare well. Maths section of CLAT is pretty easy as it covers elementary maths. The type of questions each year are very similar. If you need a Separate book to prepare for Maths then you can use R.S Aggarwal.

Other than that the guide books like Universal's guide to CLAT or Arihant's CLAT manual also cover the maths section sufficiently.

You need not spend too much time on maths as compared to other section as the weightage is also less. Also, make sure you look at the previous year question papers and practice those questions well.

Best of luck