Open the in-game information panel
Look for the help, paytable or information control before spending money. Record the RTP figure and any configuration wording shown there.
Compare like with like
The same title can be offered in different configurations. Compare the exact game version, provider and operator information rather than relying on a screenshot from another site.
Ask the operator
If the figure is missing or unclear, ask support for the configured RTP and keep the written answer. Do not play until you are satisfied with the information.