Actual hours field on work order labor grid (P13732)

 Hello, We are implementing CAM for refinery maintenance processes. The standard process of capturing labor costs on the work order using time writing functionality (P051121) is being mapped. 

But there is a field on the work order labor grid for actual hours for each labor task. How can we utilize this field? Is there any other way of capturing labor costs for a work order. 

Regards, 

Laxmikant