You mean the twelve digits on the second line, right?
First two digits: a code number for the fab plant where it was made. 23=Austin, TX (I think)
Next two digits: year code (99, 00)
Next two: the week it was fabbed.
My Athlon: 230015...... Fabbed this year, week 15, in Austin
As for the remaining numbers, beats me. Maybe a serial number of sorts?