Any time you do a steroid cycle, it will shut down your natural production. It may contain everything you need for the cycle, but as far as I have seen, they don't also contain your PCT. PCT starting time depends on the gear you are using. Some requires more wait time, to let the esters clear. A standard PCT looks like this :
wk 1
Clomid 100mg ED
Wk 2-3
Clomid 50mg ED