I received the 1,000 V-Bucks for joining the Fortnite Crew but not the other 950. Why not?

When you first sign up to join the Fortnite Crew you will either receive the Battle Pass or 950 V-Bucks if you have already purchased it. The 950 V-Bucks are to cover the V-Bucks already spent on the current Battle Pass.

Note: This is a one-time payment per season. If you did not already own the Battle Pass when subscribing to Fortnite Crew, you will not receive a 950 V-Bucks credit.