What is the “Cancel buys on sell fills” setting on the Settings – Main tab of the MoonBot terminal for?

In the MoonBot terminal on the Settings – Main tab, the parameter “Auto Cancel Buy – NEVER / After XX Seconds” works as follows:
a) checked: If the first order in the Buy order grid is executed and a Sell order is placed, the remaining Buy orders in the grid will be automatically cancelled.
b) unchecked: If the first order in the Buy order grid is executed and a Sell order is placed, the remaining Buy orders in that grid will not be cancelled.