Finding the Run Incremental Backup check box on Synthetic Full backup type

I have an existing Schedule Policy which under its Backup Task Options, there is a check box that allows Run Incremental Backup under the Synthetic Full radio button when selected. 

I would like to create a similar Schedule Policy with the same Run Incremental Backup option. But when Editing the Tasks for its Backup Option, I don’t see the Run Incremental Backup check box option. The diagram shows the Existing Schedule Policy which has the option at the top, and the newly created Schedule Policy which does not provide that option at the bottom. 

I suppose a workaround is for me to create a clone of the existing schedule policy and make the adjustments. But I would still like to know what is involved when creating a new Schedule Policy to have the Run Incremental Backup option on Synthetic Full backup options.