How quick did your results come back

Hey ladies I have a quick question. For those of you that took an at home pregnancy test, how quickly did your test go positive? 
Mine went positive like within seconds and I've always heard it takes a minute for the results to show up. Then I went to the doctor and he said his nurse said "I lit up the pregnancy test" whatever that means. 
So now I'm sort of thinking could the high HCG levels possibly be twins?