Hi - the BSP win LSP is calculated by:
a) adding all BSP prices where the result is a win
b) Deducting the sum of all runners (including wins, since the BSP returns include 1 point for the stake).
Non-runners are of course excluded in (b), since these would not have a stake or a result.
I suspect you may not allowed for non-runners (they are not an event so no unit stake should be placed), hence the difference in your final result. All calculations are made on the server overnight each night, the program has been running as above for over 2 years.
However, regarding your question on trends, it is correct that the trend is moving towards a zero pandl over the past year - most of the profit was made in the first year.
The method largely involves looking at price discrepancies between bookmakers and betfair in pre-racing markets for horses near the top of the market.
Smart markets is usually informative for looking at horses that have attracted some early interest, but I suspect there are more false positives now than when smart markets started.
