Waiting time has one sided tolerance or two sided tolerance?

In service industries ‘waiting time’ is often an important quality characteristic. Does waiting time has one sided tolerance or two sided tolerance?

Ans: Waiting time has one sided tolerance, as while service of car technician often said it will take fifteen minutes to service. It means we have to wait maximum for fifteen minutes or car will be ready with in fifteen minutes so, he is providing us only an upper specification limit. Therefor waiting time has one sided tolerance. 

Same as while online purchasing a product mostly service provider said product will be delivered in 3 to 5 days. It means we have to wait maximum for four to five days or product will be on door within four to five days so, he is providing us only an upper specification limit. Therefor waiting time has one sided tolerance.