diff --git a/django/db/migrations/questioner.py b/django/db/migrations/questioner.py
index 32fa40db082..0315df06307 100644
--- a/django/db/migrations/questioner.py
+++ b/django/db/migrations/questioner.py
@@ -130,7 +130,8 @@ class InteractiveMigrationQuestioner(MigrationQuestioner):
                 "we can't do that (the database needs something to populate existing rows).\n"
                 "Please select a fix:" % (field_name, model_name),
                 [
-                    "Provide a one-off default now (will be set on all existing rows)",
+                    ("Provide a one-off default now (will be set on all existing "
+                     "rows with a null value for this column)"),
                     "Quit, and let me add a default in models.py",
                 ]
             )
@@ -149,7 +150,8 @@ class InteractiveMigrationQuestioner(MigrationQuestioner):
                 "populate existing rows).\n"
                 "Please select a fix:" % (field_name, model_name),
                 [
-                    "Provide a one-off default now (will be set on all existing rows)",
+                    ("Provide a one-off default now (will be set on all existing "
+                     "rows with a null value for this column)"),
                     ("Ignore for now, and let me handle existing rows with NULL myself "
                      "(e.g. because you added a RunPython or RunSQL operation to handle "
                      "NULL values in a previous data migration)"),