Hi, I am being taxed for education assistance received from my employer. How can I calculate how much imputed income will come out my paychecks?

I have requested more than $5,525, anything over that amount I will be taxed (which is what is happening now). However I have now paid more than half of what I requested in paycheck deductions. I am confused on if I am being taxed or just paying for the semester via my wages.