Darrentax

I have been medically retired from work aged 42 and receive a pension from my employer. Using the HMRC website via my government gateway account, I can see that I have the standard allowance plus blind persons allowance £12570 + £3070). I then have deduction (£5135) due to underpayment (which is correct) but an additional deduction of £4779 for 'state pension'. My total deductions are then £9914. I am not entitled to state pension until 2050, so I need to understand why it forms part of my deduction. Help please.