Cannot change some fields in line item of FI document

Hello all Guru,

Could you help me explain this point?

Confusion: Some fields are set in OB32A but they cannot be changed in actual document.

T-code : OB32A

Some fields are set for change in line item as amount, order, cost center, profit center

However, in actual  document, I cannot change them because all of them are grey out

Could you help me explain this case clearly?

Hope for your reply as soon as possible.

Thanks so much for your time.

Le Thi Hong Van (Ms.)