They are more or less the same. They are good enough for schools to consider you and focus on your full application. Neither will hinder you and the second does not show a large difference. Go enjoy your time at your current school and the ECs you are passionate about. The rest of the year is just for you. You have done what you can for M10.
It means that for one who has taken the same standardized test more than once that the highest section score from among all of the sittings will be used to create the highest score possible from all of the applicant’s sittings for that test. In OP’s situation, the math score from the second test (92) would be substituted for the math score in the first test (87) resulting in a higher overall score for the applicant than either the 87 or 89.