The estimated delivery date for a reward is the date by which you expect to deliver that reward to backers. If you're offering more than one thing in a single reward tier, set your estimated delivery date to when you expect everything in the reward tier to be delivered.
Estimated delivery dates are mandatory for each reward tier, so be sure to choose a time frame that you feel confident in fulfilling.
Setbacks are possible with any project — creative ones especially. When the unforeseen occurs, creators are expected to post a project update explaining the situation. Sharing the story, speed bumps and all, is part of the Kickstarter experience.
If you're continuing to run into fulfillment problems, feel free to reach out to our Support team so that we can better assist.