The number of full time pupils on roll with a nursery class type should be less than or equal to the sum of nursery pupils on roll.
The census determines 'part time' based on a flag on the student profile > extended tab, not attendance codes.
Check these flags have been set correctly by using the Group Updater
Go to Admin > Students > Group Updater > Select the Year group > Student attribute: 'Part Time Student'
Students showing as False are NOT flagged as part time.
Students showing as True are flagged as part time
Update any students who are recorded incorrectly and then recalculate your census to clear the error.