I like to see it in context of the Service (impact of the Service/Product). 
It could be a business critical Application that is affected (maybe a salary payment system) , but the payments are done 3 days of the month. So only those 3 days it is Critical. 

A laptop issue is normally not critical (impact low) unless it is for a VIP user (?)

impact/urgency is in context if the service/product/impacted audience/time.