Well, I ‘m not so experienced but watching my games as other games so far I started believing that :

Possession : is considering the quality and condition of the players, presence of the managers, tickets, friends, formation, maybe home field or out, maybe win bonus and giving a balance. With that, we can’t be sure who ‘s gonna win the game, it’s like when a bookmaker gives % and bets for a team to win the match.
Total shots : the real process of the game. Considering less factors, like q, formation/orders, maybe form of the players. This is the first judgment . The team with more shots it’s usually the winner.
Shots on target-shots – shots efficiency : it’s the capability of the attackers against the defenders. Considering the q of the players, the form, maybe a special ability – meaning a ST with one-to-one against a GK with no sa has better chances against a ST with no sa, against a GK with o-t-o sa.
Passes completed : I don’t know how this thing is working.

Of course here, we have the “luck” factor, sometimes the program favors one team. A 4* team has good chances against a 5* team but sometimes the program can favor also 2* dif. quality (if we suppose that all other conditions are ok). With that it’s trying to keep the interest on the game and make a simulation of real football.

All these things are behind the curtain – the program and the process.
During and after that it’s what a manager can see. The visualization, the mask, the picture of the match. The game must give a variety of the progress of the match. Here comes (sometimes) the fails. Like the example I gave. By random process, the program presented 2 penalties & red cards in two minutes.