Instance is a running strategy enabled for an instrument/timeframe. The Running Strategies tab indicates the complete list of instances.
Max Open Deals: Maximum number of open deals the strategy can open in one running instance.
Multiplicator: The following formula applied to calculate next deal volume:
Multiplictor is applied to Buy and Sell open deals separately.
Example: Initial Order Volume = 10K, Multiplicator = 2
If the initial order volume is changed then next deal volume is calculated based on the new order volume, there is no volume recalculation for deals opened before.
Both strategy parameters: Max Open Deals and Multiplicator mostly used in combination for so-called Martingale strategies.