I was wrong that I post this in other forum part.

I was surprised when I saw and realized that go rules at your server are unfair! There is no komifor white player.
This rule means that white player should gain 6.5 points more because his opponent begins the game. For example if black has 100 points in the end of the game and white has 96 points then white player should win the game (100<96+6.5=102.5). The amount of komi considered as many as 6.5 points because statistics of matches between world best players show this decision most fairest of all. If komi will be 5.5 that black has more chances to win, 7.5 - white has, 6.5 - most suitable condition, equal chances.

Other thing I want to say is the board size. 15*15 is very non-standard size for go games. 19*19 is the most popular, but 13*13 sometimes also may be used. But komi on 13*13 is usually equal to 5.5 points, rather than 6.5 on 19*19 board.

I hope, you will fix it as soon as possible.