There are several factors that determine how offensive distribution settings translate to shot attempts in a game. First, keep in mind that not every player possession ends up in a shot. The player may also turn the ball over or get fouled.
Also remember that the distribution points are relative to the other 4 players on the court during a given possession. For example if you set four players to a 1 and one player to a 10, the player with 10 is going to get far more than 10% of the shots while those 5 are on the floor. In fact, he'll get about 71% of the shots (10/14).
Second, you have to look at minutes played. The more minutes he plays, the more shots he'll get - So FGA should be looked at on a per minute basis, not on an absolute basis. You also have to factor in offensive rebounds and steals as both can lead to shots that are not part of the normal offensive sets.
Additionally, play-by-play should be looked at to determine how many possessions that particular player was fouled without resulting foul shots, as well as how many possessions led to turnovers. These are all possessions that will not yield FGA.
You also have to look at double-teams. When one or more players are double-teamed, that will lead to (normally) less shots for the double-teamed players, and more shots for the non-double-teamed players.
Next you need to look at FTA. A player who is fouled does not get charged for a FGA. So if you see a player who had 10 FTA, that's roughly the equivalent of 5 more FGA.
Finally, there is just random chance. On each possession your offensive distribution weightings are evaluated and someone will take the shot based on those numbers - But that is done on a possession by possession basis, which over the course of a season will balance out, but may lead to more or less shots in an individual game.