apt-get upgrade question

[Penn Gwynne <Pen.Gwynne@verizon.net>]

Last week I upgraded a stock woody install to KDE 3.1.1 using Ralf's debs.  
Everything went very smoothly and I am very happy with it - only one or two 
anomalies.

Tonight I did an "apt-get update", "apt-get upgrade" and it said it would 
upgrade 45 packages.  I picked  "n" and then did "apt-get -s upgrade".  As I 
KDE relevant packages were targeted.

An excerpt of the print out is:

Inst libc6-dev (2.2.5-11.5 Debian-Security:3.0/stable) [ ]
Inst libc6 (2.2.5-11.5 Debian-Security:3.0/stable)
Conf libc6 (2.2.5-11.5 Debian-Security:3.0/stable)
Inst kdelibs4 (4:3.1.1-0woody3 Official build of KDE for Debian stable:stable) 
[ ]
Inst kdelibs-bin (4:3.1.1-0woody3 Official build of KDE for Debian 
stable:stable) [ ]
Inst kdelibs-data (4:3.1.1-0woody3 Official build of KDE for Debian 
stable:stable)

Using kdelibs as an example, the version to be installed is stated as 
4:3.1.1-0woody3.  (what does the "4" mean?)

From this I assume that the update will come from Ralf's site and that doing 
an upgrade should be ok.

Is this a safe assumption?

Thanks,
/Pen