I'd take the 200 sq yards bit with a pinch of salt. (Not literally).
It claims to be 6 times more concentrated, but I think most of us would put down more than 6 handfuls of ordinary manure per sq yard.
Put another way, would 6 bags of ordinary manure of the size indicated cover quite a large plot? You may have paid £30, but I bet you got more than 6 bags of manure.