“Generally30 seconds is added to stoppage time for each individual substitution made during a football match, according to BBC Sport and RefChat. If multiple substitutions occur during the same stoppage, it is counted as one opportunity, although the referee may add extra time if the process takes longer, notes TheFA.com.
Standard Rule: 30 seconds per substitution.
Contextual Time: If a player takes too long to leave the pitch, the referee can add more time.
Multiple Substitutions: Multiple substitutions by a team during the same stoppage count as one, but the referee will account for the total time lost.”
So basically, the more substitutions you make the more time you give the opposition to score.
Conversely it gives you more time to score too. But if you’re taking off your forwards and replacing them with defenders that would seem less likely”
