Each Grade showed the approximate strength of the creature, it wasn't any kind of exact value since two Champion Grade monsters could have completely different strengths.
However, they were necessarily more powerful than a Terror Grade monster, if they were not, then an incorrect grade was given.
A mistake was only possible with Champion Grade and Terror Grade, and only if those monsters were not part of the Chaos Hearth. In that case, even an inexperienced Oracle could understand what Grade monsters were in it.
Those who weren't Awakened yet and especially those who weren't even aware of it, could make mistakes. They judged the opponent based on their appearance, first attacks, and their feelings, but for Awakened Ones, everything was much simpler.
"Hah, you know you spread the energy in your body rather unusually." Toruf smirked as his eyes narrowed.