user: Question: How many different numbers of total dances are there for the couple ranked at number 6?
Columns: ['Rank by average', 'Place', 'Couple', 'Total points', 'Number of dances', 'Average']
Types: ['real', 'real', 'text', 'real', 'real', 'text']
Sample row: [1.0, 2.0, 'Gilles & Cheryl', 449.0, 16.0, '28.1']
SQL:

assistant: SELECT COUNT("Number of dances") FROM "Table" WHERE "Place" = 6.0;