If something comes up and you can no longer make the time you scheduled your exam for, you always have the option to reschedule your exam for any other open time slots!
From RegisterBlast, locate the History section and find the test you need to make changes to. Click "Reschedule" to begin the process.
On the rescheduling page you will be given two options, similar to what you encountered when you first registered.
Pick a new date and time for your exam. As the testing center is open from 8am to 8pm, during normal hours, pick a time that works best for you! Be careful, as time slots can fill up quickly and rarely open back up!
Click "RESCHEDULE" to confirm your selection. No further steps are needed and your exam has been set to the new time/date you selected!