Your message is confusing.

Are you on the professional account? If so, shipping is handled through templates which you find under Shipping Settings.

You must create various templates and assign them appropriately to your SKUs.

You say you don't "have the template" yet also say choices are only 15-28 days -- which sounds like it must be a template choice.

If your only transit time choice for Standard is 5-28 days, you must be shipping from outside the U.S.