Resource Instance assignment in Report Resource transaction, to charge and required fields becomes 0

Summary:

We have created resources and resource instances in manufacturing , and the resources are set to be Automatically transacted , while assigning the resource instance in the Resources for the particular resource , the "Required" and "To charge" fields gets automatically set to zero , so is this the expected behaviour , can we set the system such that even after assigning resource instance it automatically update/ do not change the above two mentioned fields.