- Not available on that edition (the reason is in the tooltip)
- Depends on the setting, your class or another addon (details in the tooltip)
What it does
Checks a count taken over your party or raid, always including you: the whole group, the members holding an assigned role, or the dead members, as a number of players or as a percent of the group.
Why you might use it
Count what is happening in the group and react to it. For example, switch to a mass-resurrection or cleanup rotation once more than half the group is dead, or use a different opener with fewer than five players. Tanks, Healers and Damage dealers count the members whose assigned role is that one; a member with no assigned role is not counted under any role. Tick "As a percent of the group" to compare a percent of everyone, you included, instead of a number of players. A member the game cannot report makes the count unavailable rather than too low. Assigned roles do not exist on Classic Era and Burning Crusade, where the role counts are unavailable. See also In Group and Class In Group.
Example
the percent of your group that is dead or a ghost is greater than 50 percent
Settings
What each setting in the condition editor means, from the game's own help.
Counts the players in your party or raid, always including you: the whole group, the members holding an assigned role (Tank, Healer or damage dealer) or the members who are dead or ghosts. Tick the box to compare a percent of the whole group instead of a number of players, for example more than 50 percent dead. Alone, the group is 1 player. A member with no assigned role is not counted under any role. A member the game cannot report makes the count unavailable rather than too low.
Operator - How to compare Group Count with the Value value. This comparison uses basic mathematical comparison operations.
Value - A number of players, or a percent of the whole group when the box is ticked. You are always part of the group and of every count you fit.