what are the 0-6 in chkconfig result ?
chkconfig --list|grep iptables iptables 0:off 1:off 2:on 3:on 4:on 5:on 6:off
The different numbers correspond with the different runlevels for that service.
Wikipedia has a detailed explanation on the different runlevels (they can also vary in meaning depending on the base system) if you need more specific information.
These numbers are indiacate runlevels decides which process or program to be executed at startup. All these things are defined in /etc/inittab. Linux distributions has seven different runlevels and at the time of startup init process checks which runlevel is running and on the basis of that it executes the process and services. In the boot procedure init is the last step which is responsible for the execution of services.
Runlevel is a system state in which typically the advanced administration over Linux can be done by switching between them.