I'll be the first to admit population demographics were not my are of study at university haha. That number seems really low to me, but okay, let's use it. if the 1000 students at Hogwarts represent 5.4% of the wizarding population that gives us a total wizarding population of 5.4 million wizards.
Whoa... what? If 1000 people is 5.4% of the population, there are probably around 19500 wizards. Where do you get 5.4 million? I.. what?