Sorry for a possibly stupid question, but I'm confused.

After a recent trip to Hong Kong, and discovering that I was unable to read a "Give Way (让) sign, I decided that I'd like to learn traditional versions of simplified characters I already know.

I selected "Simplified and previously added Traditional", but I'm not really sure what this means.

Does it mean that after I've "learned" a simplified character, the traditional version will be added? If not, what does it mean?

Thanks for your help :)

It means no NEW traditional will be added. Traditionals that were added before will still be reviewed. Simplified will be added and reviewed as usual.

Oh right.

So what I want is the "Both" option?

Yes. Welcome to the ranks of seasoned "both" learners who get to appreciate how efficiently Skritter lets you do both styles! (Efficiently but with some bugs though...)