Board Thread:Manga Discussion/@comment-5967049-20150219202823/@comment-34865947-20180302001652

I believe the E in permanence for SPTW is because when he stops time he is referred to SPTW and can only hold the time stop for 5 seconds thus the low durability. This is also why the regular SP has an A in permanence because physically he is very durable. This also explains the drop in growth potential from A to C. Once he increased the time stop to 5 seconds, the growth potential dropped because there was only so much more he could increase the time stop by.