This article is in the Control section of the App.
From the Control page, find the heading Incentives under Configuration on the left-hand sidebar.
This will take you to a list of available incentives and you can see which ones are applied or not in the list:
Click on the button next to the STC incentive.
In this section of the Incentives page you have the capability to change the STC incentive price which will be used in the calculation of the financials for the proposals which are generated.
You can also change the number of years that it will be applied after this year which will also change the financial calculations for the proposals.
Once you have finished editing, then ensure that you press the button at the bottom of the page.