Congratulations On Marraige What Is The Deal With Those Internet Popups That Say "You Are The 999999th Visitor-congratulations You Win"?

What is the deal with those Internet popups that say "You are the 999999th visitor-congratulations you win"? - congratulations on marraige

For years I have seen these ads on the Internet who say: "You are the 999,999 th visitor, congratulations on winning?" By clicking above, you must fill out this form. Besides, what is the meaning of being the 999,999 visitor or a Web site? If that were true, we should not wait until they can reach one million visitors?