Need to share the actual mileage as under.

Need to share the actual mileage as under. City mileage - 6 kmpl Highway-10 kmpl. The company claims an average of 18 kmpl, while the other YouTube influencer mentions 14kmpl in the city. But while we are using we are shocked to have a mileage of 6 kmpl in the city. Also to share, the vehicle while at red lights drops the mileage by 2kmpl more but while driving to comes back to 6kmpl. I thought and made up my mind with even 12 kmpl in the city with tight traffic but now with 6kmpl, I am finding myself stressed about my investment.