Redmine

I tried to add 2 days delay to the TaskB which follows taskA. TaskA due date is 2018-08-03 (Friday) (YYYY-MM-DD). After adding the delay TaskB start date is 2018-08-06 (Monday). I expect 2018-08-08 (Wednesday). I think it added the number of days as delay not the number of working days. Is there any other way to add number of working days as delay?

Thanks,
Karthick