group_group.txt how this column works

[Osiek 0]

Hello, I got one question.
What does last row in group_group.txt mean/do?

Mostly it's value one, sometimes it's low values <10, but for ores it has strange values.
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Group    spider3_04        
{            
    Vnum    2704    
    1    2074    6
    2    2075    4
    3    2076    2
}

 

Group    deposit_1        
{            
    Vnum    2001    
    1    20049    35
    2    20050    30
    3    20051    20
    4    20052    15
    5    20047    18
}    

[Sonitex 1677]

Its probability for that particular group to spawn. If you do not define it, it will be set to 1.

Pretty much the same concept as in special_item_group.