Was it exactly 4 months? Here's a 3-part answer:

1: Assuming the car is owned by an individual (not owned by a business), the registration expiration month is the same month as the car's owner's birthday.

2: The inspection also expires on the same month. So, suppose your birthday is 10 months from now, and you get the car inspected. It's going to expire in 10 months.

3: Now, to answer your question. Maximum for a sticker is 16 months. That's why I asked. If you went in for inspection 4 months and 1 day too early, your sticker will expire in 4 months. But if you go in 3 months at 29 days too early, then you should get a 6 months sticker. NOTE: Your exact birthday doesn't matter; only your birthday month matters.