The Global Army had become quite proficient at checking the attunement with mana, but that only applied to humans and mortals.
If anything, the attunement with mana was a human construct that only served unevolved warriors. That stat became useless after reaching one hundred points, and science had yet to learn how to classify beings standing past it.
Khan was a special case, which worked both against and to his benefit. His attunement was incomplete, so that stat could still work to evaluate his power and track other features. However, his uniqueness also made it unreliable.
Garret had adjusted scanners and developed innovative procedures that could track Khan's attunement despite his very inhuman status.
Nevertheless, Khan was now asking something as precise as ninety-nine point nine-nine percent, and his request didn't stop there. His scientists finally connected the dots, understanding that he wanted to train until he reached that exact number.