Petrol fuel efficient with company promised milleage

June 2019 I bought new BS 6 baleno zeta petrol. 10000 km i used only short distances , milleage use to be 14 to 15. Full tank , it will go 400 to 450km Last week I have been to trivandrum , from mangalore (650 km) . I filled petrol from kerala( full tank). It was sufficient to reach mangalore. After that i refilled again my tank in mangalore. Tank was full by 29 litres. That means there was some 5 - 7 litre remaining in tank after 650km.,(tank capacity - 37 litres). Millege is 22km/l approx. We where three passengers in car, and two suitcase and some other things. Entire stretch AC WAS ON. IT WAS NON STOP DRIVE TILL MANGALORE. CONS - BODY IS VERY LIGHT, gear not free as my old etios PROS SILENT LIKE BATTERY CAR, GOOD MILLEAGE