Chapter 83: Re-entering the Scholar Palace, Continuous Treasures Found! _3
The difference between eighth and ninth grade was primarily in the expansion of abilities within the domain of intermediate spells.
A proper eighth grade upper (Spirit Bridge Perfection) would generally have multiple intermediate spells or secret techniques at perfection, and might even create their own spells, breaking through the Nine Revolutions limit. When these abilities were combined, their combat power would be naturally higher.
A proper eighth grade lower (Late-stage Spirit Bridge) would typically have multiple spells or secret techniques at the ninth revolution.
From ninth to eighth grade, the primordial energy didn't transform qualitatively, it only made the physical body stronger. Of course, the difference between the eighth and ninth grade martial artists was significant, but the difference among the magic professions was smaller.
As for whether a single spell at the ninth revolution counted as eighth grade combat power, it depended on the situation.