To change the default permission level for a specific project in a subsite in SharePoint, you should do the following:

1. Step 1: Open the project subsite in SharePoint.


2. Step 2: Go to the ‘Settings’ tab > ‘Site Permissions’.


3. Step 3: Click the ‘Settings’ button.


4. Step 4: Scroll down to the bottom of the ‘Custom Permission Levels’ list.


5. Step 5: Select the permission level that you want to use as the default.


6. Step 6: Click ‘OK’ to save the changes.