When I had to replace my old Mazda 121 Metro, I chose the Holden Trax because it was meant to be fuel-efficient. The manual is claimed to get 7.0 L/100 km, but in reality mine is getting 8.77 L/100 km. That's pathetic. I had more power, speed, and economy in my Metro.
The claimed fuel economy figure is a result of a standard test that all carmakers have to conduct. It's intended to give buyers a guide they can use to compare cars when choosing which to buy. The figure will differ in real world due to all the factors that can influence fuel economy in everyday driving. I would persist with it, you could find it will come down with more miles on it, and you could look at your driving habits and see if you can make any changes that might cut the fuel useage.