A matrix (cross-product) report is a cross-tabulation of four groups of data: One group of data is displayed across the page. One group of data is displayed down the page. One group of data is the cross-product, which determines all possible locations where the across and down data relate and places a cell in those locations. One group of data is displayed as the "filler" of the cells.
Product Order property The Product Order property specifies the order in which groups are evaluated in the cross product for a summary. Product Order also defines the frequency of a summary, formula, or placeholder in a matrix (cross-product) group. That is, the summary, formula, or placeholder has one value for each combination of values of the groups in its Product Order. Product Order is used only for columns owned by cross-product groups. Because a cross product relates multiple groups, the groups in the cross product could be evaluated in any one of many different orders. Therefore, when creating a summary for a cross product, you must use Product Order to specify for Reports Builder which group should be evaluated first, which second, and so on. You must also use Product Order to specify the frequency of a summary, formula, or placeholder within the cross product.
Reset At property The Reset At property specifies the group at which the summary column value resets to zero (if Function is Count), null (if Function is not Count), or Value If Null (if the column has one). Reset At has a list of values containing valid reset groups. Reset At determines if the summary is a running summary or a periodic (e.g., group-level) summary.