You need to file a 2021 Form 5329 showing an excess contribution of $6,000 and a 2022 Form 5329 showing this $6,000 carried in from 2021 plus the $6,000 excess contribution for 2022 for a total excess of $12,000. The actual amount of the penalty will depend on the timing of the contributions and the December 31 account value each year.
The penalty is based on the amount of the excess contribution or the year end value of the IRA, whichever is less. The amount of contribution for a particular year that is made after the end of the year by the due date of the tax return must be added to the actual year-end value, so if the $6,000 contribution for 2021 was made in, say, February 2022, the penalty is on $6,000 even though the actual December 31, 2021 value was zero.
Having made the $12,000 distribution first, it's not clear if the distribution of the remaining $935 constitutes a return of the entire $6,500 contribution made for 2023 or not. I'm not aware of any IRS guidance on correcting excess contributions made over multiple years when the present value in the individual's Roth IRAs is less than the total of the excess contributions.
