The 4-day invoicing lock applies to only notes for billable activities. Non-billable activities aren't invoiced so the process that allows 4 days to elapse between when the note is approved and when it's eligible to be batched into an 837 or set as ready for manual invoicing if the claim is to a manually billed payer does not apply. However, even though the note for a non-billable activity is not invoiced, once the note is approved, the note lock applies and for the average user, there is no option to edit that note except as follows: 

Writers who approve their own notes have the option of rescinding that approval by clicking the link to do so from the Notes to Unapprove module on their home page but they must do so before the nightly update processes are completed. Simply put, if they click the submit button today, thereby approving their note, they must unapprove it that same day.  Once that window closes, it requires an admin's intervention to return the note to an editable status. 

Writers whose notes are subject to review and approval may pull back their own notes the same day they submitted them as long as those notes were not already picked up and approved by the reviewing supervisor by clicking the link for that note in the Notes to Unsubmit module on their home page.  Once the note has been approved, it's locked and requires an admin's intervention to return the note to an editable status.