According to ESPN.com's Rob Demovsky, the fine stems from Bennett pushing Seahawks linebacker K.J. Wright in the fourth quarter of the game after Wright contacted Packers quarterback Aaron Rodgers while he dove headfirst at the end of a run.
After the game, Bennett explained why he got so physical with Wright:
"It's my quarterback. I've always got his back. It's a bad penalty at that moment in time, but I thought it was a cheap shot. I saw him out of my peripheral, which isn't the best all the time. I always protect the quarterback. I'll never let anybody take a cheap shot on my guy. That's any guy on the team. I've got everybody's back."
Although the penalty cost Green Bay 15 yards, Rodgers got a first down on the play, and the Packers managed to run out the clock on that drive to preserve the win.
Green Bay signed Bennett in free agency during the offseason after he spent the 2016 campaign with the Super Bowl-winning New England Patriots.
In his Packers debut, the former Pro Bowler made three receptions for 43 yards.