Why does updating the w.dwl file change the f/w version?

I have a Q2686 which responds as follows to ati3:
ati3
660_09gg.Q2686H 1952244 030806 18:53
OK
I wanted to update to V06.61 and for this I had the files w.dwl, dwl.dwl and C61b_q2686h.dwl. I first loaded on the w.dwl file which I believe is the EEPROM parameters file. When I did an ati3 after this it responded:
ati3
661_09gg.Q2686H 1952244 030806 18:53
OK
I don’t understand why the version number had changed when this was just EEPROM parameters and more perculiarly, why had the version number changed but the time and date stamp hadn’t?

When I downloaded the C61b_q2686h.dwl firmware file and did ati3 I got:
ati3
661_09gg.Q2686H 1925236 100506 11:13
OK
which now shows an updated time and date stamp.