Immunization & Hosts file entry questions

First Immunization. (I am running V1.6.2 in "Advanced Mode" under Windows XP 32bit.) When I select the "Immunize" button in the left-side menu, a screen appears with a green "progress bar" expanding left-to-right across the top of the page. At the same time, in the upper right corner, a "counter" displays results for "Unprotected", "Protected" and "Total". I understand immunization involves adding entries to the system Registry, and it works through my browsers (Firefox & IE8). But:

1.) What are the "things" being counted?

2.) Why does the "Unprotected" number always grow from zero (immediately after immunization) then, after several days/weeks of system use, the "Unprotected" number "counts" back down to zero during re-immunization?


Now, Hosts File Entries. When I select "Tools" in the left-side menu, then "Hosts File", there is a green "cross" in the top menu labeled "Add SB S&D hosts list". I have been "clicking" on this green cross after each SB S&D scan session, and this adds a "prepared list of websites known for bad behavior" to my Hosts file. Does this action result in literally adding/appending a new list each time, so the Hosts file grows and grows in length. Or, is it a "replacement" list that may be few entries longer (or shorter?) each time?

I believe that it just looks for entries in the Spybot hosts file that aren't in it yet, and then adds them; I made a thread about it over a year ago, and I'm about to update it with my latest findings:D:
http://forums.spybot.info/showthread.php?t=61429