diff --git a/src/wagtail_personalisation/forms.py b/src/wagtail_personalisation/forms.py
index d7c2fee..6046ec0 100644
--- a/src/wagtail_personalisation/forms.py
+++ b/src/wagtail_personalisation/forms.py
@@ -87,7 +87,7 @@ class SegmentAdminForm(WagtailAdminModelForm):
         if not self.instance.is_static:
             self.instance.count = 0
 
-        if is_new:
+        if is_new and self.instance.is_static and not self.instance.all_rules_static:
             rules = [
                 form.instance for formset in self.formsets.values()
                 for form in formset
@@ -113,18 +113,20 @@ class SegmentAdminForm(WagtailAdminModelForm):
             User = get_user_model()
             users = User.objects.filter(is_active=True, is_staff=False)
 
-            take_user = takewhile(
-                lambda x: instance.count == 0 or len(users_to_add) <= instance.count,
-                users
-            )
-            for user in take_user:
+            matched_count = 0
+            for user in users.iterator():
                 request.user = user
                 passes = adapter._test_rules(instance.get_rules(), request, instance.match_any)
-                if passes and instance.randomise_into_segment():
-                    users_to_add.append(user)
-                elif passes:
-                    users_to_exclude.append(user)
+                if passes:
+                    matched_count += 1
+                    if len(users_to_add) <= instance.count:
+                        if instance.randomise_into_segment():
+                            users_to_add.append(user)
+                        else:
+                            users_to_exclude.append(user)
 
+            instance.matched_users_count = matched_count
+            instance.matched_count_updated_at = datetime.now()
             instance.static_users.add(*users_to_add)
             instance.excluded_users.add(*users_to_exclude)