Room Capacity with Couples in Longwise Sets.
The diagram shows a rectangular floor (16yd (14.4m) wide by 17yd (15.3m) long) with Couples disposed as for Longwise sets:
the leftmost line (A) shows the unnumbered Couples having just come onto the floor at the announcement of the dance;
the next line shows them Made up in four Sets (B1-B4), each of four Couples;
the next line shows them Made up in five Sets (C1-C5), each of three Couples;
the rightmost line shows them Made up in three Sets (D1-D3), each of five Couples.