Where does each font apply? See below some examples:
Font weight 300 (light)
Mainly for everything related to descriptions:
Font weight 400 (regular)
Applies for most of the main texts: Booking details, dates, features or calendar pricing.
Font weight 500 (medium)
Applies for the Call to Action and main texts: Search and select button, suggestions, labels, product naming, pricing as well as information on the enhance your stay and confirmation screen.
Font weight 600 (semi-bold)
If added (as it is not mandatory), it will replace the "Medium" in certain areas: Terms of use, the step of the booking process,