I just walk the dance thrice,
so everyone knows their shadow.
The mathematics, for the caller:
Counting couples,
if you are out (not facing another couple)
then YOUR-couple is that # couple.
E.g, you and your C#1 are at the end of the oval.
When the oval rotates, you are out --so YOU are
your own C#2.
Rotates again; your lefthand couple is your C#3, etc.
OR: The oval 4 times,
leaving your couple out;
making it your own C#4.
Hence your current NBR is your Shadow.