The CPP/QPP COLA preference is the annual rate at which future Canada Pension Plan (CPP) and Quebec Pension Plan (QPP) benefits will increase.
The setting in Plan Preferences, to the right side of the Preferences screen, will apply to the client case that you are presently viewing. This assumption can also be edited on a per scenario basis within the client case.
The setting in System Preferences, to the left side of the Preferences screen, is used only as an initial default in newly created client cases. System Preferences serve only as a template set of assumptions. When you create a new client case, a copy of the System Preferences will be written into your new client's Plan Preferences.
Plan Preferences vs. System Preferences
Changes to this setting on the mirror Default Inflation / Growth Rates panel in System Preferences, on the left side of the screen, will be used only going forward, as you create new client cases. System Preferences are used as a template only for new client cases. Changes to System Preferences will not retroactively affect your existing client cases.
If you want to change this preference in any existing client cases, you will need to open and edit them individually, in each case's Plan Preferences.