user: Question: How many tariff codes have a bts retail price of 2.553p/min?
Columns: ['Scheme', 'Tariff code', 'BTs retail price (regulated)', 'Approx premium', 'Prefixes']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Pence per call, fixed at all times', 'ff15', '5.10p/call', '7p/call', '0871, 0872']
SQL:

assistant: SELECT COUNT("Tariff code") FROM "Table" WHERE "BTs retail price (regulated)" = '2.553p/min';