The SRCOP of €32k for the year is allocated monthly as €2666.
If you have unused SRCOP from previous months, which you should as based on your post it appears your normal monthly salary is €2000 leaving you with €666 unused, that is also available.
Presuming this is your March salary, you cumulative SRCOP for the 3 months is €7988 and your salary for the 3 months is €8400, so approx €400 is taxable at 42%.
However, based on the amount of tax deducted, it appears you may not be on a cumulative tax cert but on week 1 basis, which basically means any unused SRCOP doesn't get carried forward and you get taxed at 42% on any excess over the €2666.
If you are on a week 1 tax cert, which is noted on the cert, call Revenue to a cumulative cert issued so it can be rectified in your next payslip.
Sorry - post crossed with Bazermc's