This depends upon how you (or if you) have set up the calendar. If you go to 'options' >'brewing', you will find the viewing options for the calendar. You can set this to display 'all recipe folders', the 'main recipe folder', or 'brew log only'. You can also specify to set the calendar only to show those recipe where you are listed as the brewer.
If you use the brew log function for the recipes that you are brewing, it is pretty easy to set up. Then only those recipe in the brew log will be visible on the calendar.
If you want the calendar to look at recipes in all the folders or the main recipe folder, then you need to set the dates on all the recipes to distant past (I set my recipes to 1/1/2001 when creating them). This way they will not appear on the calendar (or actually will appear if you click back using the 'way back machine'.
Likewise, you can specify only to show those recipes where you are the brewer and leave the 'brewer' field blank on all your recipes which you are not scheduling to brew.
Personally, I find that using the 'brew log' and placing copies of the recipe into it when I am scheduling to brew them is the easiest way to use the calendar. It also makes it easy to see the recipes that I have scheduled, track brew dates, and separates them from the master copies in my main recipe folders.