Slippage amount, in points (dollars per share or contract), for each transaction that simulates a market order filling at the open
Any formula specifying dollars per share or contract (points)
Defines the amount of slippage to apply to each market-at-open transaction, in price points.
OpenSlip is applied to any transaction that logically occurs at the open and not at a specified limit or stop price.
If OpenSlip is not specified then Slippage is applied instead.
Note that OpenSlip will be applied to limit or stop orders when the fill is at the open but not at the limit or stop price, i.e., when the open gaps beyond the specified price.