This would indicate that you have fewer than 95% of students listed with an enrol status of Current (single registration at this school). If this is correct as this is just a query you can annotate this to confirm when uploading your census to Collect.
If you do not believe this is correct you can check the information held by going to Admin > Students > Group Updater and amend the student attribute to enrol status and choose.
In the present value:
C Current (single registration at this school)
G Guest (pupil not registered at this school but attending some lessons or sessions)
M Current Main (dual registration)
S Current Subsidiary (dual registration)
P Previous