Cast on 65 for desired circumference with these two yarns. Held light fingering yarn double along with the faux fur yarn held single.

Instructions state to cast on 55 st and work in the flat to length, garter st, then join the ends with a seam. It’s much easier to join it and work in the round, st st.

If one works out an actual guage, one can extrapolate how many stitches are needed for the desired circumference.

The guage for the pattern states 19 st US 10 / 4”. Mathematically, that will give the expected 12” width.
Luzia yarn guage is stated as 12 st US 11.
Ones actual guage in Luzia with a US 10 will be around there as well. If one casts on 55, the width will be ~ 16”, which may be desirable, provided one has enough yarn. It’s hard to tell the actual width from the photos. If one wants the 12” width, one should cast on 36 - 40 st, working flat and seaming. Provisional cast on is ill advised for faux fur yarn because it’s hard to see the stitches. Regular seaming of cast on and bound off edges will not be detectable.

There must have been quite a few extra yards in the fingering sk, because I actually used ~ 500 y, but I have ~ 1/2 sk leftover.