If you try to look up 5150, it comes back with several possible ideas. It could be the Van Halen album from the 80s, it could be used in reference to a Dell Inspiron, it might be police code for something. Here's what we found out about Dierks Bentley's 5-1-5-0. According to Wikipedia, 5150 is an involuntary psychiatric hold. Basically, that means a police officer or doctor or someone can hold someone down if it seems like they have a mental disorder that could be dangerous to themselves or the people around them.

This is why the Van Halen album was called 5150 so if you guessed that, you're partially right.

Normally it's pronounced 'fifty-one fifty' but as 'fifty' doesn't rhyme with much, Dierks Bentley changed it to 'five one five oh' so it could rhyme with 'po-po', forever changing the way we say 5150.