Alt Condition base value in sales order
we have an existing alt cond base value 656 assigned to three cond types ZT11, ZT12 and ZT13 in sales order. There are different cond base values determined for ZT11, ZT12 and ZT13. My questions are :-
1) how it is possible to assign one alt cond base value routine 656 to three different condition types. For ZT11, the cond base value is custom field A as an example. For ZT12, cond base value is custom field B of sales order and for ZT13, cond base value is custom field C of sales order as an example.
I need to know how is the system able to differentiate which alt cond base value from custom fields A,B and C is determined for which cond type since base routine 656 is same for all the thee condition types ?
2) when the billing is done for the above sales order, in the billing document the same alt base value routine 656 appears for ZT11,12 and 13. I need to know how is the system differentiates between a sales order routine 656 and billing alt base routine 656. i mean , the structure for sales order is komk/komp. Is the same pricing structure used for billing ?