Viewing smartgroup shows less results then editing the smartgroup

I created a new smartgroup starting from a participant search between two dates and in a certain event type. This gave 402 results. When I save this search as a smartgroup and then view the contacts in this group I get 320 results.
When I then edit the smargroup search I can again see 402.
If you need more information just ask me. It would be great if this problem could be solved.