Just call the number on the form and reschedule. I think the limit is at least three weeks and no more than 6 mos. for the next jury duty. I just rescheduled it earlier this year to June 2nd, but seeing that I’m starting a new job on June 2nd, had to reschedule again and they had no problem with it.
Here’s a hint: schedule for a Monday or Tuesday since they won’t have the cases for the week set up yet, you are supposedly less likely to be picked.