Sheridan Consulting uses the cash basis of accounting and a fiscal year ending December 31. Beginning on September 1, 2016, Sheridan performs services for Culver International at a rate of $ 4200 per month. On February 12, 2017, Culver pays Sheridan $ 21000 in full for all services rendered from September 1, 2016 to January 31, 2017. Sheridan understated revenues by ________ on its year-end financial statement.