What do ratios like 8: 1, 2: 1, 1.5: 1 mean in bookmakers? How to calculate the size of the fees using these ratios?

Read more about it here: https://medium.com/amoveo/working-principles-of-prediction-markets-through-the-prism-of-a-bookmaker-23af654601e0?source=friends_link&sk=2c550ef6b4a75156f3c9bd0ae4a3a586