Im so confused about kickstarter finalization

So I pledged the $20 tier which entitled me to a copy of the game on Mac or PC.

Now im on the page where I have $20 to spend on a reward.

Is "extra retail key" a code to get the game when its released or something?

Also what is a "game loaded USB key" cause I can select that also which is $20.

Im so confused as to what im supposed to chose

You shouldn't have to choose anything. At the top, it should say you have the $20 bundle, everything else costs extra money. At the end of the list, it should show you how much credit you have ($20) and how much you've spent (which should be $20 because of the $20 bundle). It will then subtract the credit you have from how much you've spent and tell you how much extra you have to spend (which should be $0). If you add something such as a USB drive (which you can only do at the $95 and higher pledge levels anyway) then it will add $20 to the total you have to pay through the fulfillment site.

you will see at the top of the page, your current backer bundle, ie. $20 bundle in your case, and below that are any extras that you might want to purchase in addition to your bundle, shirts, extra game keys (unlock additional copies of the game on official release), extra beta keys, etc...

a "game loaded USB key" is a usb fob loaded with a copy of the game

if you just want your $20 backer game copy with no extra's then you shouldnt have to do anything, just fill in your Credits Name and any other details it asks for and your done

Just got my finalization email today.

Completing the finalization was absolutly smooth.

I had pledged 250$ tier + 20$ for USB Key + 15$ for international shipping => 285$

When logged on the finalization screen, ican see i have 285$ to spend, 250$ being allready used for the tier i have applied for.

I just had to spread remaining 35$ as i wanted to (keeping in mind that 15$ had to be kept for international shipping). So this meant i had to spread 20$.

I simply selected the 20$ USB Key, then finalized by providing my mail details.

I forgot to choose the correct size for included T-shirt. But this is not a big deal.

The finalization site is really fast and clear. I know a few of you may have problem, but UBER has really done a great job to make everythin clear.

Well done UBER !