How does extra copies from bundles/packs work in steam?

i read it also and it's a good chance you'll get a gift copy of css and even if you don't it's still a good price for all of the other games

No giftable Counter Strike Source.

I had a voucher gained from a previous purchase, so I got the pack for 18.75.
I just had to have it, although it would've been great if I could have gifted the extra CSS away.

Edit: if anyone else is buying it, then use this voucher: SPOOKY-TREATS-GMG20X to get 20% off and get the complete valve pack for $20

No extra copies. Gift copies on the Valve pack are specific to Half-Life 2 & Half-Life: Ep 1. I had Portal 1 & 2 before adding the Valve Pack, no gift copies granted. This is common on most of the packs, you get the additional items but just loose any duplicates. I got Saints Row 3 Complete from a bundle after I had Saints Row 3 Standard. Just added all the DLC, again no extra gift copy.

Well add a game you already have to your cart and read the Warning you get all the games you get an extra copie of are mentioned on that external page which's link is in that warning