It does depend from the date kcc receive the letter. My forms where received by KCC in 1st week of September, my case number became current in November, but my interview is sheduled for March.
Every time i was calling KCC - I was told that my forms were not processed yet, until last week when I found out the date of my interview.
Although they were saying it takes about 6 to 8 weeks to process the forms, it took them 18 weeks to process my forms.
Conclusion: Send your forms as quick as possible, but check every entry 100 times cause errors might cost you more then an interview on a later date.