GroupsBeforeRowHeaders Element (RDL)
Indicates the number of instances of the outermost column group that appear outside the row headers.
The minimum value for the GroupsBeforeRowHeaders element is 0. The maximum value is 2147573647.
A subtotal column in a matrix is considered a part of the last detail column; that is, the rightmost detail column in a matrix that reads left-to-right, and the leftmost detail column in a matrix that reads right-to-left. The subtotal column moves with that column.