Do I get less Contritbution if I do a humble giveaway?

Here's how it works:

When you do a contribution, you get the store value of the game. The amount you pay for the bundle is irrelevant (Steamgifts has no way of knowing!) So you can, if you have withered black heart, pay $1 and get full value for all of the non-BTA games!

But there's a catch. Of course, Steamgifts doesn't want to encourage people to exploit giveaways like that. So the total lifetime value you can get from bundles is capped at $30. After that, bundles can only count as %20 of your non-bundled value. So if you give away a lot of bundle games and nothing else, your CV will rise to $30 and stop there.

If you then give away a non-bundle game worth $10, your CV will raise by %12, to %42, because you get the $10 from that non-bundle game, and %20 of that ($2) worth of bundle-value can now be applied to your CV. (This assumes you had $2 of 'locked' bundle-value left above that $30, of course.)

Does that make sense?

It's the rules, if you only use humble games it is going to stop adding, no matter how many more humble games you add

Giving a full bundle does give max contribution.

yes. gifting it "honestly" as the bundle for basically the price of the bundle doesn't count as "bundled" with the asterisk. it added those 6 cv as straight value.
its only when you gift a bundle game that cost a fraction of a dollar as if it cost 20 that the asterisk comes in and nerfs it.(the bit of extra change comes from the formula of how the nerfing is done)

The extra 6 are from Humble Indie Bundle #3. Keys for entire bundles seem to be valued based on the average paid for that bundle, and are not counted as "bundled games" in regards to CV.

Yup. I remember this guy too. :D

before the game was bundled. asterisks get backdated to the bundle's start(oddly even for bonus games added later, at least from what I've heard)