The penalty at the disconnection from game

[eSVau]

from league page:

Leaving means not finishing a game till victory screen. That means someone who is not staying till the end will be handled as leaver (indepentend of reason/cause). Leavers will recieve a penalty, which is measures time-based considering someones last 20 games.
penalty = abs( point_from_this_game ) + 50 * ( 1 - time_percentage_stayed_in_this_and_19_games_before );

An existing penalty will be reduced by 0.5 points every nice completed game. With a perfect stay time of 100% and a single leave at the current game you would get a penalty of a bit more than 10 points, which means you have to play at least 20 games to reduce your penalty to zero.