Group Condition Routine in Pricing condition type

Hi All,

while activationg group condition for a pricing condition type, I see three options

1) Overall document

2) Across all condition types

3) Mat. pricing group

As far as I know, if i select overall document then scaling will be done based on cummulative quantities of all the items coming under same pricing condition type in a sales document and for if i select mat. pricing group, scaling will be done based on cummulative quantities of all the items under same mat. pricing goup. Now what does this option 2) do? Across all condition types??

Thanks in advance

Yaswanth