Covid is pretty contagious, but you really need to be around someone for ~15 minutes to have a good chance of infecting them. Does that mean that someone has t

Covid is pretty contagious, but you really need to be around someone for ~15 minutes to have a good chance of infecting them. Does that mean that someone has to breath in my virus for 15 minutes before there's enough of it inside them to infect them? Or does it mean that if I'm the infected staff member constantly spewing virus near an ever-changing cast of shoppers, I can expect to infect about 4 people an hour, some of whom were near me for only seconds?