diff --git a/anatomy/models.py b/anatomy/models.py
index af01e257..34d5620c 100644
--- a/anatomy/models.py
+++ b/anatomy/models.py
@@ -297,7 +297,7 @@ class UserAnswer(models.Model):
         settings.AUTH_USER_MODEL, null=True, blank=True, on_delete=models.SET_NULL
     )
 
-    cid = models.BigIntegerField(blank=True, null=True)
+    cid = models.BigIntegerField(blank=True, null=True, help_text="Candidate ID (limitied by BigIntegerField size)")
 
     # Each user answer is associated with a particular exam
     exam = models.ForeignKey(