I’m very new to Scrivener, so this is probably a total newbie question, but I’m having a little trouble with the corkboard. My index cards come up with huge red letters that say “N/A” on them. I can still see my text on each card, but I’m wondering if there’s something I’ve done wrong, somehow, in my organization?
I’m not sure why it’s coming up as a default, but the red labels are what’s called Status labels. You can set them up to read anything you like (I have one that says REWRITE for when I know that I need to go back and make a scene better 
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Anyway, the way to change it is to select one of the index cards that has N\A on it, then look at the Inspector panel on the right hand side of the screen (click the blue i icon at the top right if the Inspector is hidden).
In the middle of the Inspector is a panel labelled ‘General’, and on that is an option labelled Status:
Click on the drop down and choose No Status to remove the label.
You’ll have to repeat that process for all the cards that have N\A on them, I think. I’ve not found a way to set options on multiple cards are once.
To batch change the label or status for documents, select the documents you want to change in the binder (or in corkboard or outliner), right click and then set the Status or Label through the context menu.
You can also choose to show or hide the status stamp in the corkboard using View>Corkboard and selecting or deselecting the option. And you can set the opacity of the stamp in Edit>Options>Corkboard with the slider.
And when you right-click on an item in the Binder and choose Stamps/Edit you not only see a list of the stamps from which you can delete stamps or add new ones to but you can also set one of them as the default (which now seems to be “N/A”). If you have no use for them at the moment, “None” would be the appropriate choice.
By the way, you can do the same with labels. The only difference is that in the View menu you can make the label colour visible in the Binder which can be very helpful depending on what you use labels for.
Ah, thank you, I didn’t think of looking in the right click menu.
Now I can easily label my entire NaNo novel as “REWRITE”. 
Wow. Thank you for such swift and thorough help! I just did a batch edit and changed my default to no status. I love this index card tool, by the way – and I’m loving Scrivener.