Desperate question

Friends, I need help from the pros, or rather yours.

Rather, not an article, but only a question that I cannot figure out on my own.

I recently installed a RSS feed via FeedBurner on my blog .
')
I can not figure out the numbers that he shows.

Now the counter shows 21readers? Does this mean that exactly 21 readers subscribed to the blog via RSS?

Yesterday I heard a different point of view. So, the number means how many people went to the blog yesterday via RSS?

I do not believe. Judge, please.