Revenue is przychód.
Most likely, it is the revenue that is adjusted.
cccccccccccccccccccc
Contract Revenues are tied to Costs, but Billings on Contracts are not always tied to Costs. Sometimes elements of a contract are billed in advance or sometimes they are delayed by mutual agreement (or disagreement). This mismatch between actual billed revenue and earned revenue will require an adjusting entry but since the Percentage of Completion method adjusts billed revenue to reflect earned revenue, billings are posted to revenues and adjusted later to reflect the correct earned revenue amount. (Debit Accounts Receivable, Credit Sales).
http://www.accountingunplugged.com/2008/09/11/percentage-of-...
cccccccccccccccccccccccccccccccccccccccccc

Making a WIP Adjustment
Once you know the amounts that you are over- or under-billed, the next step is to post a WIP adjustment. This will enable you to utilize the matching principal — or in other words, to match your income and expenses to the same period of time — and produce an accurate monthly P&L.
Following are the steps for posting over- and under-billings

Make sure the contract amount and the job status are correct
Make sure a budget has been entered
Make sure all change orders have been posted and have the correct status
Run the Over/Under Billings report for projects with current status with the correct posting period selected
Post the over/under billing adjustment using the correct date and posting period Note: WIP adjustments are typically “reversed in next period”
https://on-trackinc.com/work-in-process/

cccccc
At the end of the accounting period, an adjusting journal entry must be prepared to adjust the revenue recognized on jobs that are in progress based upon the estimated percentage of job completion as of that date. That journal entry is reversed on the first day of the next reporting period.
https://www.probuilder.com/how-use-percentage-completion-acc...