People do have the tendency to overstate/exaggerate the abilities of their cars when they post ads. He can put any kind of info on his ad as seller..it is the buyer's job to verify his claims. But, if he had done it here on Pakwheel forums then there are plenty of cheetahs here to fact-check his claims..
I have looked at the ad and honestly in his asking price I would rather go for something else (probably a clean 8th gen civic).
and btw 27 km/l is probably something that a Suzuki GS150 motorcycle does on highway..lol