How to modify the *Initial Due Date Option

Summary: Modify *Initial Due Date Option

Content (required): I mistakenly updated the *Initial Due Date Option as 1 instead of 30.

Do we have the option to modify that as 30 again? Please advise how to modify that option. It seems to be disabled.

Version (include the version you are using, if applicable): 21D

Code Snippet (add any code snippets that support your topic, if applicable):