In the unfortunate event of conceding a goal, You'll need to record it to keep your score updated. This can help you keep count if you concede a lot but is probably going to be more use to save you remembering the minutes of various events when completing your match report.
To do this click 'add game event' at the bottom of the screen.
You will then be shown a list of different events you can add to the match timeline.
Select 'goal against'
Make sure the time is correct, select the type of goal and then click 'opposition player' and that should load in to the match timeline.