Wang Tao discovered that if he calculated the impurity accumulation at 0.5% per Fusion Crystal Core, and if he kept only whole numbers, then these data probably added up.
Wang Tao had seen them fuse a Crystal Core before, at which time the display showed 0% Internal Impurity... In reality, it might have been 0.5%, but the figure was rounded down, and without rounding up, it displayed 0%!
So it made sense that after Xiang Hongbin had fused 12 Crystal Cores, his Internal Impurity was 6%.
Wei Zhenguo had fused seven, and his Internal Impurity was 3%, actually 3.5%! Maybe if he fused another, it would turn into 4%.
Other people followed suit, and it all matched up.
Therefore, Wang Tao came to a conclusion—in theory, the upper limit of Crystal Cores a person could fuse was no more than 200.
Because if a Crystal Core produced 0.5% impurity in the body, then 200 would amount to 100% impurity, which would definitely lead to zombie transformation.