False advertising

Today I went to Superspar Cape Gate, they advertise a 1kg Snacktime assorted crackers for R89.99, but on the box it's indicated as 800 g, when I told one of the shop assistant's that it is false advertising, she called the supervisor, who probably thought I'm stupid and weighed the box at the bakery, for what reason as it is indicated as 800 g on the box, and she's rude telling me it is a 1 kg, they added the other 200 g next to the line, but the red line.is where you tear off the cellophane to open the box.