add +1 to business_days. That should solve the issue
Use the below logic to add 1
var dc = new DurationCalculator();
dc.setSchedule('eb65c2250fc76340e1f30dbce1050ee2', 'Los Angeles'); // Schedule sys_id and system time zone
var dur = dc.calcScheduleDuration(start, end);
var business_days = dur/(60*60*9); // Update the t
var gdt = new GlideDateTime(end);
var day_of_month = gdt.getDayOfWeekUTC();
if(day_of_month < 6)
business_days += 1;
