Review cost responsibility, account classification and variance interpretation together. The account tells you what the business bought, the cost center tells you who is responsible, and the posting date places it in the period. Changing one field can change a management report while leaving the journal balanced.
These independent tasks mix cost postings with KSB1 and summary reports. Use signed amounts so credits reduce actual cost. Keep the requested account and center filters visible in your reasoning; an all-center total answers a different question. Below-plan cost produces a negative actual-minus-plan variance in this client. Nothing new is introduced here. Your job is to choose the right detail or summary view and preserve the evidence the manager needs.