This is a 4-digit number, which symbolizes that the player is no longer a beginner. S/he is a "Class E" player now. This is significant. I suggest a small celebration.
After crossing over 1000, s/he becomes much more confident in him/herself. S/he could not wait to attack the next target. It's a time when the self-motivation is strongest, and faster progress are expected. Rating jumps are very common. S/he will start gathering trophies here and there. This is the happiest period of his/her chess career.
Normally this milestone is hit soon after the first target 800, maybe after a couple of months. Overall you should expect it in one to two years since his/her first rated tournament.