How long 2 to 5 business days?

Monday through Friday are considered business days. When you are counting out the business days ignore Saturday and Sunday.
As an example, if today is Thursday and you have a package that should arrive 2-5 business days from today, You could get it any time between Monday and Thursday. 2 business days from today, would be Friday, skip Saturday and Sunday, and Monday. 5 business days is 3 days past that or Thursday.