This policy setting determines whether Windows PowerShell scripts are run before non-Windows PowerShell scripts during user ...

This policy setting determines whether Windows PowerShell scripts are run before non-Windows PowerShell scripts during user logon and logoff. By default, Windows PowerShell scripts run after non-Windows PowerShell scripts. 
 
If you enable this policy setting, within each applicable Group Policy Object (GPO), PowerShell scripts are run before non-PowerShell scripts during user logon and logoff. 

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 user logon scripts:

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

Assume also that there are two users, Qin Hong and Tamara Johnston. 
For Qin, GPOs A, B, and C are applied. Therefore, the scripts for GPOs B and C run in the following order for Qin:

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

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

Note: This policy setting determines the order in which user logon and logoff 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:
 
User Configuration\Policies\Windows Settings\Scripts (Logon/Logoff)\Logon
User Configuration\Policies\Windows Settings\Scripts (Logon/Logoff)\Logoff

This policy setting appears in the Computer Configuration and User Configuration folders. The policy setting set in Computer Configuration takes precedence over the setting set in User Configuration.