On a computer, hover your mouse over the button. If the link at the bottom of your browser looks like a long, messy string of numbers and redirects, do not click it .
While 387.21 MB could be a small video or software, it is a common size used in "dummy" files that actually contain malware or adware .
(a game, a movie, a work document)? Did a pop-up appear before you saw this button?