You set the default for the Starting Time in the Date Picker at the top of the Window. This is connected to the Start Time in the Main window as well, so changing the time in one will change the time in the other.
The field on the second line allows you to enter a whole number for the interval between the Start and End times, with the radio buttons directing whether that number is to be expressed in minutes or hours. Only whole numbers can be used here, so an interval of 1.5 hours would need to be expressed as 90 minutes. Note that the interval specified here is locked to the Starting Time in the main window, i.e., whenever you change the Starting Time, the End Time will also change to reflect this interval. However, the Starting Time is NOT locked to the End Time; you can always change the End Time without affecting the Start Time.
The third line has the field for determining the step value on the mini-calendar. Whenever you click the Add Date to Date List button on the Main Window, the selection on the mini-calendar will move forward the number of days (or weeks) you program here.
Item four is the character (or group of characters) that you would define for Event Sequencing. This value can also be edited by clicking the Sequence button on the Main Window.
The fifth item defines the time interval for calendar jumping on the mini-calendar.
The next two items allow you to choose when (or if) you want to delete your Event Notes or Location. You can have that data cleared every time you click Done or you quit the application, or both. Otherwise, Note information and Event Location will be preserved for your next launch of OddCal.
The final checkbox simply clears the Date Table whenever you click the Done - Send To iCal button. If left unchecked, the dates will remain until you delete some or all of them, or you quit the application.