The M00 is a holdover from the old Form W-4 that was used before 2020. It means married with zero allowances. But the new Form W-4, starting in 2020, no longer uses allowances, so it's not clear what M00 means now, or how it affects the employer's calculation of the withholding. Specifying married would mean a lower tax rate, not higher.
As I said earlier, it's too late to do anything about 2023. In January you can use the IRS Tax Withholding Estimator to fill out a new W-4 for 2024. You will have plenty of time to adjust the withholding so that you do not get a refund.
