Very good vehicle but unsatisfactory mileage for CVT model

I have bought a Kiger RXT Turbo CVT. I liked everything. Smooth driving, comfortable seating, very good space (including boot space), nice powerful engine (since it is a turbo). I have back pain. But even after a long drive, I didn't have any issue. The features are all good. Bought in October 2021. First service was done in January 2022. But the mileage is between 9 and 10 Km/l. within city and 13 km/l (in economy mode) on long highway drive. It is nowhere near the 20.3 km/l. mentioned in the FAQ on this site for Turbo CVT!