How Machinegunners can get a chance to advance to the next round if they will score 0 goals at next tournament?
So, second team can score 30 goals and second team will win!
Where is a logic?

How first num from answer can be little, than second.

Explain plz.

In first sample if they score 0 goals they will have a chance to win, because their opponents can score less than 30 goals (for example, 0) So, Machinegunners have a chance to win in this case (of course, not 100%, but it is not necessary, read problem's condition more carefully)

Ok, for example:
The Machinegunners played away game, scored 0 goals, and conceded 30 goals.
In this case Machinegunners team has no chances to win!

If in the home game the Machinegunners will score 30 goals and concede 0 goals then they will have chances to win.