Facts to remember when working with templates scheduled from completion
1. When inline editing the template task and changing the start (or completion) day you actually change the task constraint to Must Start On (Must Finish On) and set a constraint day. This is similar to how inline editing works for regular tasks.
2. When the template is scheduled from the completion, the constraint days are calculated from the completion day. Suppose your template's duration is 285 days and you have a template task with duration 60 days. If you set its constraint to Must Start On and constraint day to 120, you will end up with Start day 165 (285 - 120) and Completion day 225 (165 + 60). So when you edit the Start day, it is actually being interpreted as Constraint day.