1 Onset of sleep from time the lights were turned off; this is called  sleep onset latency  and normally is less than 20 minutes. ( 2 Note that determining sleep and awake is based solely on the EEG. Patients sometimes feel they were awake when the EEG shows they were sleeping.
The direct cost margin is calculated by taking the difference between the revenue generated by the sale of goods or services and the sum of all direct costs associated with the production of those goods, divided by the total revenue.
The gross margin represents the percent of total sales revenue that the company retains after incurring the direct costs associated with producing the goods and services it sells. The higher the percentage, the more the company retains on each dollar of sales, to service its other costs and debt obligations. Next Up.