Pick a game and a side, type the price you were offered, and see what it charges against every number on the site. Value means the price is two points or more under the number; fair means skip it; bad means you pay more than the number and the cut. The number is the market consensus (sign in for The System), except where Elo and the market are 10+ points apart: there the market has been right, so it is the number for everyone. A forecast, not a promise. Same math in the API and MCP.
Side
Fill from a book
Parlay grader
One leg per game. Each leg is marked against the same number as above; the whole parlay by what it pays against the chance every leg wins. Signed out, the number is the market consensus.