I think they just go for numbers of times started since countdown, and the possible number of people who might want to play (judging from their statistics), and thus TWEOTW has a lower number it needs to reach.
By the way, the thought of an actual GLaDOS@Home frightens me. That's like Shodan@Home. Brr.
Well, yes and no. The length of time it takes to fill each bar is determined by the number of copies of a game in circulation on Steam; thus, games like Kick It! and The Wonderful End of the World have shorter bars to fill and Killing Floor has a much longer one, because there's been far more copies of KF sold on Steam than Kick it!
TWEotW's bar is now complete because the ARG IRC / wiki group is choosing to focus on one game at a time, as already mentioned. TWEotW was the first target.
Progress on the bars isn't determined by number of times started, but by total playtime.
Also: potatoes (ones displayed in http://steamcommunity.com/id/tyraarane) count!
They add auxiliary power and might serve as a sort of multiplier. There's a guide to all the potatoes in the Potato Sack games http://87.238.173.111/wiki/Potato_Sources; some of them can be obtained in a minute or less. (Easiest ones reposted here, because the wiki's been up and down like a drunken yo yo since yesterday.)
Spoiler Amnesia: The Dark Descent - create a profile named "Casbah" without the quotation marks. You'll be taken to an Aperture Science login screen; use the password troubled memories.
Audiosurf - on any difficulty level, get a gold medal on the "The Device Has Been Modified v2 [as-portal]" track, which runs the first time you play a song in Audiosurf and can be found in the Audiosurf radio tab thereafter.
Super Meat Boy - die 11 times on level 4-19. Use the password death traps when prompted.
Killing Floor - find the http://www.youtube.com/watch?v=xgrNh8DZugI corpse in the Bedlam map and attempt to "use" it. This can only be done on a multiplayer map, or by hosting a "Listen" multiplayer game and running it by yourself. Likewise with locating http://www.youtube.com/watch?v=7fYgcFxyakc on the new KF_Aperture map. This one is a little easier with a second person, so you don't have to try and get the zombies to step on the Super Colliding Super Button for you. The ARG IRC has been pretty consistent with hosting runs for this one, though.
Join the Steam group http://steamcommunity.com/groups/nelipot. For some reason this grants you an extra potato.
Apparently the prediction is that we're only going to unlock the game about 10 hours earlier. Wish they'd launched this a week ago, when it could've actually made a difference.
Current estimate is http://cpucount.zapto.org/. It was at almost 26 hours early when I went to bed last night, but as many U.S.-based Steam users stopped playing the games and went to bed last night progress slowed. I'd expect to see it kick back up again as more people come online.