When entering a work log you can also adjust remaining estimate using one of 4 modes. This is exactly the same with JIRA's own "Log Work" dialog, but we are explaining here again.
- Adjust Automatically: The estimate will be reduced by the amount of work done, but it will never be below 0
- Use Existing Estimate: Remaining estimate is kept unchanged.
- Set To: Allows you to freely specify a new remaining estimate
- Reduce By: Remaining estimate is reduced by the specified value
You can also hide Remaining estimate field group and reduce log work dialog height. Your preference will be remembered and when you open the dialog next time.