Rapper Pooh Shiesty is going away for a 5-plus year stretch for shooting a nightclub security guard — and, considering what he could have gotten, he’s actually happy with that number.

Pooh, whose real name is Lontrell Williams, was facing more than 8 years in prison, if prosecutors got their way — but his attorney, Bradford Cohen, tells Olasmediatv.com … the government’s calculations were off.

Cohen says they asked for no more than 63 months, which is exactly what the judge gave him.

As we reported, Pooh was arrested last June for aggravated battery with a deadly weapon.

A police report, obtained by Olasmediatv.com, said Miami-Dade PD was called to the King of Diamonds club for a reported shooting … witnesses said security was *ing the rapper out of the building when an altercation erupted between the staff and him.

The security manager told police the beef was over cash that fell out of Pooh’s pants, prompting him to fire off a round that hit a security guard in the ankle.

He eventually plead guilty to one count of possession of a firearm in furtherance of a crime of violence.

Cohen tells us, “We are going to file a motion for any time he spent in state prison on the same crime to get him additional credit for time served.”