If you don't assume that he single star is something to do with Taurus and the group is the Pleiades then there is the possibility that the single star is one of note and the ring of stars is just for positioning....
Like Arcturus with the 7 stars next to it being the constellation Bootes (at about the 15 hour position). Then going clockwise you get Lyra (21 h), Perseus (3 h) and Cancer (9 h).
Andrew
I think it's very good to consider that the single star might be something other than Taurus.
The group of seven stars might also be the big dipper. It doesn't necessarily have to be Pleiades. There's no guarantee the shape of the group is important. If it's a mnemonic, then the number of stars might be enough to identify it to whoever created it.
Andrew -
In most of the astronomical drawings the circuit's point of beginning-and-end is marked. That was observed so long ago that I'm surprised most people seem not to know it, even now.
The 'string' in that diagram marks that beginning-and-end-point, which limits somewhat the probable identifications for those stars.
I've seen no evidence that anything in the manuscript has to do with astrology (zodiacs show the series of the month-marking constellations and - just as they do in the Vms - they offered a calendar and roster known to everyone, literate or not.
Anyway, just for completeness, the first in the following list is a sort-of astrological one because it sets the prime meridian at Aries
beginning-and-end points:
1. The lunar mansions series' last asterism is called Batn al-Hut (The belly of the fish). In astrological terms it is said to extend from 17°08'34″ Pisces to 0° Aries but of course people didn't talk that way normally: they just named the stars. (On the lunar mansions, I recommend Emilie Savage Smith, either her Islamicate Celestial Globes or a much smaller work called 'A Thirteenth-Century Divinatory Device..' (don't forget to read a later 'update' essay by her, though).
2. A very old beginning-and-end point had been the Pleiades (leaving open the possibility that the single star is actually meant for the Pole star if the string represents a prime meridian). In ancient India, it was called by the word for Victory (Thurayya) - still a tamil surname - but also the Arab name for the same asterism. It began the ancient years.
3. Then you have things like the star marking the Persian, or the Coptic, the Jewish, the Byzantine, or the Latin or Manichean New Years..
4. Or the beginning-and-end might have more to do with practical things such as the beginning of the annual circuit of Fairs, or the beginning of the liturgical calendar, or the beginning of the Mediterranean sailing season, which properly began in March and ended in November... though I found that sometimes people sailed in the off-season.
Anyway, those are a few possibilities. Do remember that neither Ptolemy nor the Arabs nor the Latins invented the stars, or observation and naming of stars. Cheers.