Should I Wait After Applying Sunscreen Before Sun Exposure?

hi i wear sunscreen whenever i am outside. mostly a spf 30. i wear one with synthetic sunscreen ingredients in it instead of a mineral one and its broad spectrum. my issue is that im ALWAYS in a rush before stepping outside and never wait 15 to 20 minutes after applying. i generally wait 10 or so minutes. is this a big issue? and has all my hard work gone down the drain?. also. can you please debunk the issue of car window tinting. is being in a tinted window car protecting against the sun?.

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