You may need to make analytics changes on your booking confirmation page and be unsure whether they belong on the HCS side. The answer depends on which website the booking checkout is on.
Why this happens. HCS builds and manages your main property-listing WordPress website. If bookings complete on a separate Hostfully-hosted checkout page on a different subdomain, such as reservations.yourdomain.com, that page is fully controlled by Hostfully, not by the WordPress site HCS built.
What you can do. If your checkout is Hostfully-hosted, make analytics changes for the booking confirmation in your Hostfully account settings, not in the WordPress site. If you are unsure which setup you have, look at the URL that appears when a guest reaches the ‘booking confirmed’ page after payment. If it is on a different domain than your main site, that checkout is Hostfully-hosted.