Alto 800 [LXI 2020 model] poor mileage

I recently brought an Alto 800 from True Value. Total run 40k and it got recently serviced as well.

From the day I have brought it, I have put full tank fuel and the last bar starts blinking at 300 kms. Which means I barely get 10kmpl as average.

I am really worried with the low mileage. My drive is on the city traffic only with AC. I took the issue to service center, they changed spark plugs and cleaned the throttle body but nothing worked.

Any suggestions will be really appreciated. Thanks