There's some files in /etc/init.d/ directory:
$ ls -al /etc/init.d/ | grep -i depend
-rw-r--r-- 1 root root 2739 Feb 17 05:20 .depend.boot
-rw-r--r-- 1 root root 2221 Feb 17 05:20 .depend.start
-rw-r--r-- 1 root root 1855 Feb 17 05:20 .depend.stop
Whenever you run update-rc.d the files will change. .depend.boot file is for S level, .depend.start is for 2 3 4 5 levels and .depend.stop for 0 1 6.
In my case, I have the following order in .depend.bootstart:
TARGETS = killprocs motd nvidia-kernel nfs-common rsyslog privoxy virtualbox
linuxlogo acpi-fakekey binfmt-support fancontrol openvpn hddtemp cgconfig
dropbox-container dbus dnscrypt-proxy pulseaudio atd cryptmount exim4
qbittorrent-nox ddclient acpi-support smartmontools ssh ntp loadcpufreq acpid
cron rsync cgrulesengd cpufrequtils bootlogs bootchart-done single rmnologin
rc.local stop-bootlogd
You can also see why the order presents in the way you see above. Each next line looks like this:
cgrulesengd: rsyslog cgconfig
which means that cgrulesengd needs rsyslog cgconfig to be started prior.