For adopted animals, there is a threshold that is set in your shelter's configuration that determines how many days after an adoption a return is still considered a return and when it becomes an "owner surrender" instead.

 

For example, if your shelter's threshold is set at 30 days, this means that within 30 days after the adoption, a return will be considered an "adoption return," but after more than 30 days has passed, the return will be processed as an "owner surrender" instead.

 

This threshold is set at 30 days by default, but it can be updated in Configuration by someone with configuration permissions via Configuration > General Shelter > Return/Surrender Threshold.