Emma Engineering Group receives royalties on a technical manual written by two of its engineers and sold to a publishing company. Royalties are 10% of net sales, receivable on October 1 for sales in January through June and on April 1 for sales in July through December of the prior year. Sales of the manual began in July 2015, and Emma accrued royalty revenue on $30,400 of sales at December 31, 2015. Emma received royalties of $2,889 on April 1, 2016. By what amount will Emma debit or credit royalty revenue on April 1?