user: Question: How many numbers have sp of 20/1 and a finishing position of Fence 19?
Columns: ['SP', 'Number', 'Horse', 'Age', 'Handicap (st-lb)', 'Jockey', 'Trainer', 'Owner', 'Colours', 'Finishing position']
Types: ['text', 'real', 'text', 'real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['7/1', 26.0, 'Cloudy Lane', 8.0, '10-11', 'Jason Maguire', 'Donald McCain, Jr.', 'Trevor Hemmings', 'Green/yellow quarters, whites sleeves and cap', '6th']
SQL:

assistant: SELECT COUNT("Number") FROM "Table" WHERE "SP" = '20/1' AND "Finishing position" = 'Fence 19';