Celery generates / comes in the Process screen with an existing pensioner and older month to process, why is that?
Dit you maybe add this pensioner with an original start date in the past? Because in that case, Celery reminds you this way you still have to process these months in the past for this pensioner.
However, if you do not want to (re)process these older months, for example because you will add the retroactive payment in a current pay run, you should generate these older pay runs from the past and choose 'Process as nil' for this pensioner (see print screen below) and finalize this pay run.
After that, Celery will not show this pensioner and older months any more when clicking on Process.