This policy setting determines whether Windows PowerShell scripts will run before non-PowerShell scripts during computer ...

This policy setting determines whether Windows PowerShell scripts will run before non-PowerShell scripts during computer startup and shutdown. By default, PowerShell scripts run after non-PowerShell scripts. 
 
If you enable this policy setting, within each applicable Group Policy object (GPO), PowerShell scripts will run before non-PowerShell scripts during computer startup and shutdown. 

For example, assume the following scenario: 

There are three GPOs (GPO A, GPO B, and GPO C). This policy setting is enabled in GPO A. 

GPO B and GPO C include the following computer startup scripts:

GPO B: B.cmd, B.ps1
GPO C: C.cmd, C.ps1

Assume also that there are two computers, DesktopIT and DesktopSales. 
For DesktopIT, GPOs A, B, and C are applied. Therefore, the scripts for GPOs B and C run in the following order for DesktopIT:

Within GPO B: B.ps1, B.cmd
Within GPO C: C.ps1, C.cmd
 
For DesktopSales, GPOs B and C are applied, but not GPO A. Therefore, the scripts for GPOs B and C run in the following order for DesktopSales:

Within GPO B: B.cmd, B.ps1
Within GPO C: C.cmd, C.ps1

Note: This policy setting determines the order in which computer startup and shutdown scripts are run within all applicable GPOs. You can override this policy setting for specific script types within a specific GPO by configuring the following policy settings for the GPO:
 
Computer Configuration\Policies\Windows Settings\Scripts (Startup/Shutdown)\Startup
Computer Configuration\Policies\Windows Settings\Scripts (Startup/Shutdown)\Shutdown