The HotFix numbers are read as follows:
The first digit is the last number of the year
The second, third and forth digits are the number of the day of the year (the Julian day)
The fifth is the ServicePack release. (GA = 1, SP1 = 2)
The sixth digit is the build number.
For example 235-561:
in 2012
on the 355th day of that year
for ServicePack 5
and it was the 1st Build
235-561 was released on Dec 21, 2012