The FA handed Marinakis the suspension on Friday for improper behaviour during Forest's 1-0 home loss to Fulham in the Premier League on September 28th, after the commission ruled he was guilty of improper conduct.
The commission explained the reason for Marinakis' ban, saying there was "no excuse" for such an "an egregious display of disrespectful behaviour" that could "fuel disrespect towards match officials."
Referee Josh Smith, assistant James Mainwaring and fourth official Tim Robinson said they saw Marinakis spitting on the floor towards them as they headed to the dressing room.
Marinakis said the incident was unintentional, citing a cough from smoking cigars, but the commission dismissed this, noting no mention of coughing in officials' statements and backing it with CCTV footage.
The commission concluded that Marinakis deliberately spat in contempt, classifying it as serious misconduct deserving of a significant punishment.
Marinakis suggested a ban from the tunnel and dressing room, but the commission rejected this, given his limited need to be there after games.
Another commission's written reasons said Forest manager Nuno Espirito Santo and midfielder Morgan Gibbs-White were suspended for using offensive language towards match officials after the 2-2 draw against Brighton & Hove Albion on September 22nd.