A soccer game is 90 minutes in length. But so-called effective playing time (how many minutes the ball was actually in play) may be as low as 60 minutes or even far less. This is why as referees, we must prevent time wasting by players. But sometimes we contribute to time wasting.
Look at the video below. The referee correctly calls a foul (although he misses the tactical nature of the offence and fails to issue a card) and brings the ball back to where the restart should be. Even though the wall is clearly too close, he moves away. A few second later, he comes back to move the wall back. This resulted in about 30 seconds of time lost.
In this situation, there was no quick free kick to be taken. It was going to be a ceremonial restart. The referee should have moved the wall back once the ball was set.