We added a new feature, free invitation periods. As you can see, your invite number is written X+10.
That means every user receives 10 invitations, and these will be used firstly. If you invite more than 10 people in this period, you start using your normal invites (gathered earlier by the known methods). If you don't invite any people at all, once the period is over, your normal invites will stay.
The first invitation period will last from 22.07.2009 to 05.08.2009 and the number of invites given to each is 10.