Crit as in stinger?
I'm not sure where you got the numbers from but I'mma take stuff from the DMM wiki here:
Stinger is a RNG type skill. When it procs (chance is unknown), it adds a set 20% bonus to crit frame attack up. Each stinger weapon will have it's own roll for this: example with 2 crit weapons, you can get 40% crit up.
Increasing the skill level does not increase the value of this crit up. Instead, it increases the proc rate of the skill.