what does mean last 2 digit of the serial number ?

[Bill Manning]

% There is a point named serial number in the named.conf configuration
% 
% for example 2000062620      ; serial number
% 
%  first 4 digits mean the year
% 
%  06 means the month 
% 
%  26 means the day
% 
%  And what does mean 20 ?
% 
%  Thanks 


It might mean that there have been 20 changes in the day.
Or your interpretation may be wrong and there is zero relationship
to dates, i.e. its just a randomly generated, monotonically increasing
string.  
The main point being that the serial number is not a date.

-- 
--bill