I don’t know any kanji, but I do recognize 万 as 10 000, and the image read 1100万, so I’m pretty sure it should read ”exceeded 10 million leib” not “exceeded 1 billion leib”, as that would be a ridiculous amount of money.
If you are so dumb you convinced yourself that the elemental magic and body enhancement magic that could easily kill C-rank monsters (serpent wolves and the bird one) aren't strong even for a self-proclaimed "average" F-rank adventurer, then it will definitely not be detected as a lie.