Yes, it makes sense, elizabeth. Highlighting a certain phrase/section won't quote only that phrase/section because the quote feature quotes the entire post. If you only want to quote a certain part of a post and you click on "quote", you'd have to edit out all the rest yourself.
A simpler way to quote only a certain part of a post is to highlight that part, copy it, click "reply", paste what you copied into the "Post reply" window, and then surround what you've pasted with the quote tags.
In other words, if I only wanted to quote the phrase "when I try to post with a quote I get the whole post" from your post, I'd do the first four things I just mentioned, and then I'd do this after I'd pasted what I'd copied:
[quote]when I try to post with a quote I get the whole post[/quote]
so I'd get this in my post:
when I try to post with a quote I get the whole post
I hope that helps.