I'm thinking people in Westeros and Essos know or ought to know math such as basic geometry and probability and maybe some basics of finance, economics, physics, engineering, technology, medicine or statistics
Theoretical mathematicians today study things like group theory, number theory, probability theory, functional analysis, harmonic analysis, etc.
There are of course statisticians and applied mathematicians whose research are used in finance, economics, physics, engineering, technology, medicine, statistics and the like.
My guess is that 'mathematician' is a broad term used to encompass experts in finance, economics, physics, engineering, technology, medicine or statistics much like a 'philosopher' in ancient times studied a lot of things including math, physics and economics.
Perhaps LF means 'statistician'.
Any other mention of math as a study or the profession of 'mathematician' in the books or series? Any word from GRRM or Benioff & Weiss on what it means for a Westerosi (or Essosi) to be a 'mathematician' ?