Oftentimes, when the inside or outside decision is in relation to the top of the penalty area (the line parallel to the goal line), then the lead AR may be able to help the referee (of course, the AR may be too busy with an imminent offside decision). But if the question is about one of the vertical penalty area lines, the decision is 100% on the referee.

So if you suspect that there may be a challenge by a vertical penalty area line, adjust your positioning. Otherwise your inside/outside decision may not be correct.