iPod touch iPod Touch Syncing Apps

[MomoRacer]

Hi,
I have an iPod Touch 2g, and I just recently noticed something when i synced it with iTunes. It deletes any apps on my iPod touch that are not checked in the Applications list in iTunes. Is that a hardware setting( it's jailbroken) or is it something I've checked or unchecked.
Thanks for your help.

 

[wardev]

its the fact that it's unchecked.