There's 27 circles in the image above, and the moon has a rotational period of 27 days!
The Moon has a rotational period of 27.3 days that (except for small fluctuations) exactly coincides with its (sidereal) period for revolution about the Earth. As we will see later, this is no coincidence; it is a consequence of tidal coupling between the Earth and Moon. Because of this tidal locking of the periods for revolution and rotation, the Moon always keeps essentially the same face turned toward the Earth (small fluctuation mean that over a period of time we can actually see about 55% of the Lunar surface from the Earth).
http://csep10.phys.utk.edu/astr161/l...moonorbit.html
I don't know what it means, if anything! Just wanted to point it out!