SP is 'starting price', The officially declared starting price, calculated by taking an average of the odds offered in the betting ring when the race started is taken as the odds to use in calculating returns on all bets where no other odds were agreed at the time of the bet being placed. This is most significant in accumulators; where the bet is to forecast the winners of two or more races, the payout being on the various odds multiplie. Without 'getting' or 'knowing' the SP the bookmaker cannot calculate his payouts and potential liabilities; so it means to get or know information vital to making a decision or planning something.