@Rada0 Are you familiar with using the Help Center articles for getting answers to many questions? I typed "travel credit" in the search and found the following article:
I have a travel credit of $20 from referring a friend on Facebook. I'm about to book a room in Lisbon Portugal for a 5 night stay. How is that gonna work because I here from others the travel credit they earned didn't go to the room rate reduction when they applied?