I love these (Torah) questions (hence I’m coming out of hiding for this one)
Moshe took Micha out either right at yetzias mitzrayim (up to a year before) or before he went to midyan (he was in midyan for 40 years I think, not withstanding the midrash) so either he was 40 or 1 by parshas shlach (it makes more sense after he came back because that was when the babies were stuffed in the wall) so micha was 1 when they left mitzrayim and not between 20 and 60, those that would die in the midbar