Your math was wrong this time. Even if N95 masks are not 100% or 95% effective, still they should reduce the chances of getting infection by 95%. The real problem with most of those masks is that they usually do not fit correctly so the aerosol get inside from sides. The worse are those with ear rubber bands. But those without filter in general are bad, too. I got no COVID with 3M FFP2/3 with filter, maybe I was lucky... but for me they worked