This article gives several reasons why we wrap the tefillin around our arm 7 times.
Do the 7 windings start from the "half" intial wind that begins from the bottom of the "loop" that the strap comes from, (See the 1st wind in the picture, below) or is that one excluded and does it have to be complete "full circle" windings around the arm?
(In the picture, below, it looks like that 1st one is excluded, as there are another 7. But, I'm not sure if there are different minhagim regrading this.