Online gaming and sports betting contributed heavily to a double-digit percentage increase in gaming revenue for the city’s nine casinos last month. Total gaming revenue was $338.8 million, an increase of 13%, in August compared to the same month last year, according to figures released Thursday by the state Division of Gaming Enforcement. This summer’s total gaming revenue was up 11.6% over the same three-month period in 2018. “These results show there is a great deal of customer interest in Atlantic City’s offerings and operators have made strides adjusting in a competitive environment,” said James Plousis, chairman of the Casino Control Commission.