Typically, exporting from Booking Calendar to Google Calendar isn't directly supported. However, there's a workaround:

• Open the settings for your specific Google Calendar.
• Select "Add calendar" and then choose "From URL."
• Define the URL to the .ics feed from Booking Calendar.
  You can find this URL on the page: WP Booking Calendar > Settings > Sync > "Export - .ics" page.

Please note: Google Calendar imports events from such .ics feeds only twice per day.