Well, not that this is correct, necessarily, but a plain reading of that sentence is simply the date you actually renounced with the proviso that it was later confirmed (e.g., if the renunciation was made in person on July 1st but not confirmed until October 1st, then the effective date should be July 1st).
See https://www.irs.gov/instructions/i8854#en_US_2021_publink10001536
[note the "earliest" of the dates]
"The date you renounced your U.S. citizenship before a diplomatic or consular officer of the United States (provided that the voluntary renouncement was later confirmed by the issuance of a certificate of loss of nationality)"
yes but does this mean the date of filing or the date it was processed? I read it takes a few months to process
Well, not that this is correct, necessarily, but a plain reading of that sentence is simply the date you actually renounced with the proviso that it was later confirmed (e.g., if the renunciation was made in person on July 1st but not confirmed until October 1st, then the effective date should be July 1st).