Do, normally, only words which are eventually to be kept count, or do you also count rewrites? For example, if I rewrite a 50 word paragraph 10 times, is my daily count up to 50 or up to 500?
Why does it matter, if your word count is 50 or 500 after a rewrite? You should ask yourself, why do you want to count your words.
If you use the number to motivate yourself ("Look, I wrote 100 words. What a good day!"), then count the rewrites.
If you need the number to show someone your progress (like your publisher who pays you to finish the book), then he is probably not interested in the rewrite-count, but that's a thing you should clarify with your publisher.
If it is only for you. I would say, it does not really matter. Keep (re)writing. Every word, rewritten or not, takes you one step further to your main goal. I do not count my daily words. I only count all words of the finished novel, because I put that info into my cover letters/synopsis.
To answer to your question, I personally count only the initial revision.
The reason why: It's generally more productive to write without going back to edit, keeping all self-criticism held in until you're done with the session. Even better, wait a day or two before revising at all. You'll come at it fresh and be able to see problems you wouldn't have noticed right away.
Normally I base my word count on what's in the file when I finish my session. I don't count any minor tweaks or changes. If I spent the day rewriting a single paragraph I would end up only counting the final result.
On the other hand if I'm doing a big rewrite, like a full scene or a whole chapter I will usually count those changes. There's no hard and fast rule for this, but usually if I'm cutting out enough to save it's enough to be worth counting.
It all depends on your goal.
- If you're trying to hit a deadline by doing x words per day, then you have to compare the word count of your written work before the edit and after. Some people use pages for this rather than words.
- If you want to see how much effort you're putting in or you have a goal for each individual writing session to say "this was a successful session" or "okay, this session is done", count the words you typed.
I don't think there's a hard-and-fast rule on this, it really is up to you and what you're trying to achieve by knowing the word count.