Rocks in potting soil bags to get desired weight.

Good day. I just bought a 10kg Culterra potting soil mix the other day to plant some flowers etc. But what i found halfway in the bag was a rock about 1kg in weight. So this is what i get from Culterra 9kg's worth of potting soil. That is not a very good adverti*****t for a company that i trust in. Have a great day