Timescale from Assessment Appointment to Diagnosis?

Hi everyone, I've finally got to the end of my two year waitlist and have been given an assessment appointment for mid-February. It says on the info sheet that I probably won't get a diagnosis that day, and that I may have to wait a while for the Diagnostic Report comes through?? Any ideas on how long I might be waiting? I got myself all worked up at the thought of this being finally it, I hope it isn't too much longer now...