Calendar synced with Google: Change entries to last names instead of first names

We have our booking.com calendar synced with the Google calendar and there it shows booked days as full day events with the title "CLOSED - [customer's first name]".

We would prefer, however, if it showed the customer's last name instead of their first name. We usually adress them by their last names anyway and it would make it easier to identify them in other records.

Is there any option to change that behaviour of the calendar sync?

Thanks for any help