MRP and increase work order quantites

Hello,

I'm looking to understand how the MRP decides which work order to increase if multiple work orders are open for the same item and the demand increases.

For example:

Demand: 1500 units for 2016-02-20

WO #1 500 units - start date 2016-02-10 - requested date 2016-02-20

WO #2 500 units - start date 2016-02-10 - requested date 2016-02-20

WO #3 500 units - start date 2016-02-10 - requested date 2016-02-20

If the demand is bumped to 1700 units and the MRP generates an increase message, on which work order will the message be on and can this logic be changed if needed?