Now, you often must have noticed that the field Est. Revenue on Opportunities is either locked or is open to enter value into it.
There’s a reason for this as well.
So basically, there is a field on the Opportunity that drives this operation.
It is called as Revenue field!
If you select System Calculated, the Opportunity Lines’ Total Amount will add up to the Est. Revenue field and the field will be locked for you.
If you select User Provided, the Est. Revenue field will be unlocked with whatever value it already has and you can change the same.
It will no longer be driven of the Opportunity Lines.