Bid column

Recently my colleague uploaded the bids on shotgun in the duration column. I didn’t want this column to be seen by the department leads. Hence I selected all and from ‘Edit selected’ feature, I deleted the bid information. But the Duration that was filled automatically using the start and due dates have also gone. Is the procedure wrong? Is there anyway shotgun can lock the ones in which start and end dates are already put?

Vrisshti Singh