If your mulch bed is particularly uneven in spots, then we may have to spread the mulch at a greater depth than 1.5 to 2 inches. If this is the case, then it gives the impression that not enough mulch was spread. However, since the deal purchased calls for 500 sq ft at a depth of 1.5 to 2 inches, if the depth is greater than this, then the coverage will not be 500 sq ft. In general, this is not an issue.