I misunderstood how the button worked.

app/views/admin/application_settings/_form.html.haml

@@ -131,7 +131,7 @@
         .checkbox
           = f.label :ci_enabled do
             = f.check_box :ci_enabled
-            When checked disable CI usage until rake ci:migrate is run (8.0 only)
+            When unchecked CI is disabled until rake ci:migrate is run (8.0 only)
 
   .form-actions
     = f.submit 'Save', class: 'btn btn-primary'

doc/migrate_ci_to_ce/README.md

@@ -116,7 +116,7 @@ https://about.gitlab.com/update/
 
 After you update, go to the admin panel and temporarily disable CI.  As
   an administrator, go to **Admin Area** -> **Settings**, and under
-**Continuous Integration** uncheck **When checked this disables CI usage until rake ci:migrate is run (8.0 only)**.
+**Continuous Integration** uncheck **When unchecked CI is disabled until rake ci:migrate is run (8.0 only)**.
 
 #### 3. CI settings are now in GitLab
 
@@ -228,7 +228,7 @@ cd /home/git/gitlab
 sudo -u git -H bundle exec rake ci:migrate RAILS_ENV=production
 ```
 
-(this rake task automatically unchecks the 'When checked this disables CI usage until rake ci:migrate is run (8.0 only)' checkbox)
+(this rake task automatically unchecks the 'When unchecked CI is disabled until rake ci:migrate is run (8.0 only)' checkbox)
 
 #### 6. Restart GitLab