How to make sure Sales Orders are not considered while calculating Average Daily Demands?

Summary:

Client has some one time sales orders for some customers. But because Safety Stock is set up based on Days of Cover, plan considers these Sales Orders while calculating Average Daily Demand and suggests higher safety stocks. Plan also suggests Planned Order for that Sales Order demand. Plan does not need to suggest safety stock based on Sales Order demands because those are just one time demands, they shouldn't be considered as a trend. With this behavior, plan is trying to order more. So, there's fear of overstocking and expiring of the over-received products as they have low shelf lives.