Visible crew/equipment: The white safety wire attached to XXXX can be seen when the camera pulls up after he is dangled over the edge of the building by Eddie Temple's thugs.
Audio problem: When XXXX is drinking whiskey at Gene's flat, XXXX's mouth moves before he takes a drink but there is no sound, the audio of "You find peace with guns" is said whilst XXXX is drinking.
Continuity mistake: Dragan shoots XXXX's sniper - he is shown, dead, to XXX's right. Then, during the telephone conversation which follows, the sniper's suitcase is to the right of XXXX but the body is not to be seen.
Continuity mistake: When XXXX is dropped off by Eddie Temple he is wearing a dressing gown, but the next shot is of him in his kitchen pouring a drink wearing a T-shirt and jacket, all worked up and agitated by the news he's just heard.
Answer: Because the logo's a car registration plate and a number fits that structure better than just letters.