As for Math, most schools would view science in their world from Biomedical research. So Math may not be viewed as science by them.
If schools were following from this direction, physics and astronomy wouldn't be viewed as science.
I realized we had a similar discussion before but i will cut to the chase. Yes it is typically the safest approach to mark the science letters to be strictly biology and chemistry, and the reason is entirely due to the convenience of schools still stuck in the incorrect notion of what science is. Another very important reason is that some MD schools follow the DO/AACOMAS approach of marking math as non-science.
OP, reasonably speaking, math letters
are science letters. Any layperson will agree with you and dismiss the classification of math as non-science to be absurd regardless of what "defense" is made.
However, since you are dealing with medical schools whose scope is severely limited to
only biology and chemistry, the math LOR wouldn't be considered science. Neither would engineering, computer science etc (physics is a science LOR due to schools' odd perception that it is related to medicine in some way). Such a narrow interpretation contradicts the overall (and AAMC's) objective of acquiring applicants from every academic field.
Rather than taking a risk, i recommend following gonnif's safest approach by trying to have two biology/chem/physics LORs, a non-science LOR and a math LOR if possible. Otherwise, because the quality of LOR is absolutely critical, one science, one math and one non-science LOR is fine.