From https://college.as.virginia.edu/college-policies-regarding-majors: a student who has two majors in the College of Arts and Sciences may double count up to two courses toward the requirements for these majors. In case one major is officially interdisciplinary (https://college.as.virginia.edu/types-majors-college), up to three courses may be doublecounted. Note that major prerequisites are not requirements and are not subject to doublecounting restrictions.
For engineering (SEAS) students with a second major in math, the math department considers this situation to fall under the interdisciplinary regulation; that is, up to three courses may be double counted for major requirements.
No double counting is allowed between the math minor (or any College minor) and any other major or minor. See https://college.as.virginia.edu/minor-declaration-and-policy.