On the Category Rules screen, I see: Maximum Number of Choices and an option to "set automatically." What exactly is that feature?

M1 always tries to schedule the songs in Rank/1-2-3 order.  But your various formatting rules will regularly preclude some songs from scheduling immediately when they come to the top of the stack.  So, if song #5 is at the top of the stack and it can't fit into the next slot to be scheduled, M1 will look down to the next song.  If it passes with no violation, it will schedule that one.  Then it will try to place #5 in the next open slot of that category.  So, instead of always scheduling the songs 1-2-3-4-5, they might get scheduled: 2-1-3-5-4.     The Search Depth (maximum number of selections) gives M1 more choices for each slot.  If #1 won't fit, it tries #2.  If that won't fit, it tried #3. Generally, you want the number of choices to be about 10 to 15% of the number of songs in the category.  Thus a category with 50 songs, should have a Search Depth/# of Choices set at 5 to 10 or so.    You do not want to have HUGE search depths.  Setting the 50 song category with for Search/Choices at 30 is not good.   This because of something else you want to happen.  Say that 50 song category is designed for an 18 hour turnover.  If you have a Search depth of  5 to 10, then some song might get it's next repeat play 20 hours later...or one might get a repeat play 15 hours later, depending on your rules and such.   So you get a bit of a spread, but the repeats all come within a reasonable acceptable "window".     But if you have a big, big search depth, then in the worst case, some song might get a repeat play 5 or 6 hours later, or 30 hours later...way outside your planned rotation pattern.  This scenario is rare, but it could happen.    So keep the # of choices set at 10 to 15% of the category. If you click the button that tells M1 to set it automatically, then if you add a lot of songs to the category or remove a lot of songs, M1 will automatically adjust the setting for that category.