Dana, given that a yard is 27 cubic, two yards would be 54 cubic feet. The ST bed filled to the brim holds 32 cubic feet, that would require22 cubic feet above the bed in that "rounded off section" if there truly is 2 yards in Andrew's truck.
22 is just over 80% of 27...so that means 80% of a yard is above the box, and (just over 3/4 of a yard).
It just doesn't look to me like Andrew's load has over 3/4 of a yard ABOVE the box...unless they are "small" (not full) yards.
As said, for arguments sake, the area of the mulch above the box would have to be 22 cubic feet, and assuming there was no "hump" and the mulch was all evenly distributed, that would require a 1.4' high by 4' by 4' cube.
The mulch above the bed doesn't look at its highest point much more than 1.4', and that is at its peak and clearly it isn't that high across the whole 4' x 4' area...and wherever it's lower, that takes away from the yardage.
TJR