Guild members earn a Guild Contribution Point when they defeat dungeon and world bosses while in a party or raid, when they click the guild Attendance button, and when they complete daily guild quests that are available from Chester Douglas in Terminus.

Member's Contribution decays by -1 Contribution Point every day, at midnight during the server restart, resulting in inactive members contribution gradually being reduced to nothing.

Members can also lose Contribution Points if they are reported AFK successfully in a battlefield using the /report function, or if they quit or disconnect from a battlefield match.

I realized my mistake, you need to be in a group, then the contribution for killing a world boss or the last boss in a dungeon is counted, thanks.