In table T556R or its view - for the abs type, find abs quota types to be deducted from.
In table T556P or its view - for each of these quota types from above, check if config allows negative deduction to (field DEDUC).
In table T556R or its view - for the abs type, find abs quota types to be deducted from.
In table T556P or its view - for each of these quota types from above, check if config allows negative deduction to (field DEDUC).