An appointment is an attribute of either a Nurse or a Patient, that uniquely identifies them as either one.
At the same time, in the user guide, checkups are referred to as medical checkup appointments.

It may be more beneficial to reword at least one of these two references so as to avoid confusing users, even though I understand what was being attempted here. It may be better to change the name of the field to Status or Rank or some other attribute, but if that is too much issue, then simply removing the word 'appointment' from the medical checkups section will also do.
An appointment is an attribute of either a Nurse or a Patient, that uniquely identifies them as either one.
At the same time, in the user guide, checkups are referred to as medical checkup appointments.
It may be more beneficial to reword at least one of these two references so as to avoid confusing users, even though I understand what was being attempted here. It may be better to change the name of the field to Status or Rank or some other attribute, but if that is too much issue, then simply removing the word 'appointment' from the medical checkups section will also do.