There's no time limit. It's simply as many times as you enter the page URL, it counts it as a view. It's just how many times the URL has been accessed by users. That's about it I'm afraid.
This probably should be a comment but I'll leave it as an answer, I / someone else can convert it later.
EDIT: I'm pretty sure it's just the time connection between you and the server, and how fast it registers. If you leave and join quickly, like refreshing, it might not get time. It's not a specific time, it's just as soon as it can register that you actually got there, if that makes any sense.