The SP is typically used when bettors do not take the early prices and want the odds that are available just before the start of the race. Bookmakers calculate this based on the general betting market and the final odds offered to bettors. SP odds can be lower or higher than the initial odds, depending on market activity and other factors affecting the race.
SP Example
For example, if a horse’s odds were 4/1 earlier but shortened to 3/1 just before the race, the SP would be 3/1.