Three minutes isn't actually that short.
In those three minutes, An Jing was confident he could defeat any instructor apart from those in the 'Inner Breath like Tide' realm. Even against Inner Breath like Tide, he was confident he could take on one alone.
During this time of accumulating strength, An Jing had not only mastered his Inner Breath but had also gradually gotten a hold of the Fiend Sword Divine Skill, which awoke when he broke through his Inner Breath.
He still wasn't quite clear about what exactly this all meant.
"This is your Fate Pattern divine skill."
One night, as An Jing was effortlessly calling forth the Fiend Sword to appear and disappear, he asked the Sword Spirit, who replied, "Although it's only a part, this indicates you already possess a Fate Pattern—the more you train, the more prominent your Fate Pattern will become until it fully manifests."