The public (star) rating that a client leaves probably has very little impact on your JSS and their private rating cannot be changed. So any effect will be minimal and will not appear until the next JSS calculation.
Atif S wrote:
When does it take Effect on you JSS?
Asking clients to change their feedback is unprofessional and freelancers who do that sort of thing are the main reason we have the JSS in the first place.