If Context Type is Line Item, it allows you to choose any field on the line item shopping cart. When you select this context type, the following fields are enabled:
a. Field (Mandatory): Select a field type from the drop-down.
b. Cumulative Dimension: If you want to use a value from another dimension with the current dimension and use the resultant value as the final value, select a dimension name from the Cumulative Dimension drop-down. CPQ adds the value from another dimension to the value of the current dimension during evaluation. The cumulative dimension works only if line item field type is a number or currency.
c. Relation Type : Select a relation type between the context type and the line item field. The supported value is Related Quantity.