Understanding the numbers in package names (?OT)

[Shriramana Sharma]

i am totally confused about the numbers taking place in package names.
Only one set of numbers is obviously the product version number. I
don't understand what the others are. Here are some examples;

1. In libstdc++6-4.1-dev, I understand that 4.1 is the so-called
version number. But what does 6 mean? I have seen a file called
libstdc++.so.6 -- is this 6 and that 6 the same? What is its meaning?

2. In mysql-common_5.0.22-0ubuntu6.06.2_all.deb, 5.0.22 is the version
number. What is the 0 before ubuntu? I presume 6.06.2 is the mark of
the next point release where this package must go?

3. In mozilla-thunderbird_1.5.0.5-0ubuntu0.6.06_i386.deb, again the 0
before ubuntu. The number after ubuntu cannot be a point release
number but 6.06 is unmistakable.

4. In kgpg_4%3a3.5.2-0ubuntu8_i386.deb,
dnsutils_1%253a9.3.2-2ubuntu1.1_i386.deb,
xserver-xorg-core_1%253a1.0.2-0ubuntu10.4_i386.deb etc, some special
characters are added and numbers placed before them. Also, the numbers
after ubuntu here (8 and 1.1) are confusing.

What is the logic in this apparent mayhem?

Thanks.

Shriramana Sharma.

P.S: Since the numbers are related to development, I asked on this
list. Sorry for slight OT nature, if any.