I would treat each day individually.
Sound advice.

I would simplify by assuming that any account review not completed (one without a "completed" date stamp - is deliquent. A "re-scheduled review", therefore, is deliquent.

For example, accounts with 0 days delinquent are accounts theat were assigned the day the report is being run. Accounts that are ("minus") -7 days delinquent have been scheduled for an initial review a week from today. Those that are 30 days delinquent were assigned for an initial review last month.

If a re-schedule date is used instead of initially assigned date, then concievabley, re-scheduling could make it not deliquent.

For Monday, check for the number of delinquent accounts for that day.
On any given day, an account manager will have either contracts that were initially scheduled that day, any contractracts re-scheduled for that day and [maybe] any accounts that were rescheduled after that day.

It would seem the first priority of a "reviewer" would be to complete that days "reschedules", and then sort through that days "originally" assigned reviews.

The clear definition of deliquency is any account/contract that was not reviewed on the day it was assigned. A clear measurement of delinquency is how many days have passed since the time the the review originated and the report date.

The capacity would be measure by totaling all the "originally" (or initial) scheduled reviews + all the rescheduled reviews for the working days within the reporting range.