Fraction of a Power Statement

[RoTt35]

A character while performing a feat is stated that he had never exhibited even a fraction of that kind of power. That same character previously performed an attack calculated at 597.5 Tons of TNT, i.e. that wasn't even a fraction of his true power. Are there any standards for what value/fraction (e.g. ½) to use regarding these feats and statements?

 

[Arkenis]

Are there any standards for what value/fraction (e.g. ½) to use regarding these feats and statements?

This is probably the only real one you could use without getting wanky with it. Which would just put this character at least Low 7-C.