Different things happen when you modify a template used in Repeating Jobs depending on the version of Repeating Jobs that you use - the standard Repeating Jobs (v1) or the optional Repeating Jobs v2. 

Repeating Jobs (v1) 

You can't change a template to modify jobs in a Repeating Job (v1). 

Changes to templates used in a Repeating Job (v1) aren't shown in either existing jobs that have already been created, or jobs that will be created in the future, by the Repeating Job v1. 

If you want the changes made to the template to apply to jobs created by the Repeating Jobs v1 you must create a new Repeating Job that uses the modified template. 

Repeating Jobs v2

Repeating Jobs v2 does enable modifications made in a template to be reflected in the jobs created by the repeating job. There are some limitations to this as follows:

• You can modify future jobs that are not yet created by modifying the template used in the Repeating Job v2. When the repeating job creates the new job, it will automatically use the new template.
  
  
• Jobs that have already been created by a repeating job before a change is made to the job template won’t have the template modifications applied to them.