basically what it does it you have to be on the registration page for say 15seconds.
If a bot comes along and registers on and takes 3seconds to register and clicks register it will deny them.
but say a bot or human comes along and registers and they take 16 seconds to fill out the registration process then it will approve the registration and go onto the next step in the system(in my case email verification)
I hope that makes sense.
EDIT :: I found an addon made doing exactly what I want but it is for 3.6.8 heres the link
Is Bot: Registration Time Check