Separate the two distances
IFAB Law 13 requires attackers to stay at least one metre from a defensive wall of three or more players until the kick puts the ball in play. This is a different distance from the defenders’ required retreat from the ball.
Imagine four defenders standing shoulder to shoulder while an attacker waits beside them. The attacker’s relevant measurement is the gap to the wall; the defenders’ measurement concerns the free-kick position. A television angle showing only the kicker cannot establish both distances.
The timing explains a late run
A player may appear to be in the wall by the time the shot passes through. Freeze earlier, at the kick. Moving into the gap after the ball is in play differs from occupying it too soon. Judging only the frame in which the shot reaches the wall can produce the wrong impression.
For a replay note, identify three things: how many defenders form the barrier, the attacker’s starting gap and the moment the ball is kicked and clearly moves. The same final position can result from an early encroachment or a properly timed run. This viewing method explains what to look for without pretending a perspective-distorted image supplies a precise tape measurement.
Questions answered
Is the attacker’s wall gap the same as the defenders’ distance from the ball?
No. They are different measurements.
Does an attacker have to stay away after the ball is in play?
The wall-gap condition described here lasts until that point.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.