CentOS - Dec 2013 - chkconfig question

In the docs for chkconfig it says:

<startlevellist> is a list of the runlevels for which the service
should be started by default. Only services which are really required
for a vital system should define runlevels here. If no runlevels are
defined, a - should be used in place of the runlevels list.

and then:

More commonly, the service is off by default on all runlevels, which
looks like this:

# chkconfig: - 20 80

But services with a chkconfig entry like that are started at boot time
(e.g. mysql, httpd). So when do they get started?

On Fri, Dec 13, 2013 at 5:04 PM, Reindl Harald <h.reindl at thelounge.net>
wrote:
>
>
> Am 13.12.2013 23:00, schrieb Larry Martell:
>> In the docs for chkconfig it says:
>> More commonly, the service is off by default on all runlevels, which
>> looks like this:
>>
>> # chkconfig: - 20 80
>>
>> But services with a chkconfig entry like that are started at boot time
>> (e.g. mysql, httpd). So when do they get started?
>
> when they are enabled with "chkconfig <service> on"
>
> look at /etc/rc0.d/ to /etc/rc6.d
> chkconfig finally creates symlinks there
But at what run levels is my question.

Looking at mysqd, it has:

# chkconfig: - 64 36

and I see a S64mysqld link in rc 2, 3, 4, and 5. Why in those 4 dirs?
Will all scripts with - in the chkconfig entry be started at those 4
levels? How is putting - different from putting 2345?