The Macro Insert/Check screen simplifies the addition of macro's to your URL, you can simply build a macro by picking the option you want and adding it to your URL, or you can use one of the options to start your macro and then edit the macro by hand to add further options to your Macro.
The Input Entry box shows what you are entering and the Expanded Results shows what the resulting text will resolve to. Note: Spaces in the result will be replaced with dots for visibility because if you have 2 spaces in a path that should only have 1, it will prevent the download from working.
Macro Builder section:
Day Offsets allow you to schedule a download with a specific future or past date that will work every week, even if the date is in a different month or year.
Next or Last is available for each day of the week and the "Now (No Offset)" option will use the current date.
A good example of this is downloading a show to air on Sunday.
Putting {mt:Date:mtSun:DD} will give you the 2 digit day number of the upcoming Sunday.
Time/Date Entries is the entire list of available macro replacements.
The +/- Day Offset only works with the top 2 Time/Date entries allowing you to add or subtract a number of days from the value.
Note: this only increments or decrements the day number and will not advance a month or year. If you need to do date math for a future day, use the Day Offsets.
At the bottom of the window is a Macro box showing what the selected Time/Date Entry looks like and a Macro Result box that shows the result.
As you become more comfortable with the Macro format, you may simply type them in the URL box of your item.
Click the OK to save the changes to the entry or Cancel to not save the changes.