Match Prepartaion (Tactics)

When you set your 3 tactics, the graph shows player numbers on the right in the postion they are playing in. Is this just cosmetic or not. I currently have 3 tactics I am preparing for 4-5-1 standard, 4-5-1 defensive and 4-4-2 standard. The formation I prepare in say 4-5-1 standard shows number 9 as the 1 attacker, however my number 9 is now injured so number 15 may play there instead. When you prepare do you have to take into account the player numbers or not, can you have different numbers to the ones shown in the prepartion. This also occurs with player roles. ie in a 4-4-2 you may have an attacking midfielder in the match prepartion attacking from the centre, however he is now injured so you have to play a defensive midfielder in that position defending. The role of the prepared tactic doesnt match up. Do you need to go into that much detail

Just noticed the numbers change when you put a different player in the place in tactics screen