Supply Planning - Supplier Selection Logic for Equal Allocation Percentages in an Unconstrained Plan

In Supply Planning with an unconstrained plan, when a sourcing rule contains two suppliers with the same allocation percentage (for example, 50% and 50%), what logic does the planning engine use to select a supplier when the required supply quantity is only 1 unit?

Could you please explain how the supplier is determined in this scenario

Thank you,

Hikari Yamaguchi