The term "full-time employee" means an employee who, with respect to any calendar month in 2019, had an average of at least 30 hours of service per week or 130 hours of service in the month (130 hours of service in a month is treated as the monthly equivalent of at least 30 hours of service per week), as determined in accordance with section 4980H of the Internal Revenue Code. An employer that operated its business for the entire 2019 calendar year determines the number of its full-time employees by taking the sum of the number of full-time employees in each calendar month in 2019 and dividing that number by 12.