Red White and Bloom

So this is three days worth of progress on my Country Cottage Needleworks piece. I am also hoping to have this one done in time for July. I am really liking stitching seasonal pieces this year. The downside of this is that al my WIP's aren't getting any attention because I am moving from one new project to the next. I'm still not sure on this one that the white is showing up as much as I would like, but too late now.

And I have a question for my fellow stitchers, this may be one of those DUH questions that I really should know after 20 years of stitching. But I just don't get it. I have stitched a few Mirabilia pieces (never finished one yet), and sometimes when reading other people's blogs about them they say that they have stitched the faces "over one". Now I know what stitching over one means, but why would they only stitch the face over one? Wouldn't that make it uneven from the rest of the piece? Do you have to double each stitch to make it come out even? Am I the only one confused by this? There is probably some detailed instructions on this on the back of one of my Mirabilia charts, but have I ever read the instructions on anything! And Google just made me more confused. So I am releasing my question into blog-land and hopefully someone out there will know the answer.