debian-newbie: apt-get asks for NetInst CD

hi there

I'm new to debian, so please don't abuse me too badly.

I'm trying to install bigsister network monitoring. per the bigsister.ch page, I added the following to
/etc/apt/sources.list

deb http://software.graeff.com/debian-graeff stable main

I did this and then tried "apt-get install bigsister-agent"

The resulting output follows:

pc3:~# apt-get install bigsister-agent
Reading package lists... Done
Building dependency tree... Done
The following extra packages will be installed:
bigsister perl perl-modules
Suggested packages:
libterm-readline-gnu-perl libterm-readline-perl-perl
Recommended packages:
perl-doc
The following NEW packages will be installed:
bigsister bigsister-agent perl perl-modules
0 upgraded, 4 newly installed, 0 to remove and 0 not upgraded.
Need to get 967kB/6859kB of archives.
After unpacking 30.4MB of additional disk space will be used.
Do you want to continue [Y/n]? y
WARNING: The following packages cannot be authenticated!
bigsister bigsister-agent
Install these packages without verification [y/N]? y
Media change: please insert the disc labeled
'Debian GNU/Linux 4.0 r3 _Etch_ - Official i386 NETINST Binary-1 20080218-14:15'
in the drive '/cdrom/' and press enter

Get:1 http://software.graeff.com stable/main bigsister 1.02-4 [904kB]
Get:2 http://software.graeff.com stable/main bigsister-agent 1.02-4 [63.4kB]
Media change: please insert the disc labeled
'Debian GNU/Linux 4.0 r3 _Etch_ - Official i386 NETINST Binary-1 20080218-14:15'
in the drive '/cdrom/' and press enter

If you help me out, I would appreciate it.

Thanks.