can someone please explain what happened.

[i have crabs]

ya i know they get big.
most of what ive read sayes they max out at 30-36" in the wild and 24" in an aquarium so if he does get too big in another year ill just build bigger.i have room to turn that 300 into a 500-600 no problem
but i still think its crazy how much one grows in 1 year.
thank god i only feed them every 2-3 days