"Spread in starting time" and "no crowding" are two totally different constraints and it's important to make sure you understand what they do before enabling or disabling them.

​No crowding (two movies will never start at the same time for any scheduling day)
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This refers to the fact that you should not have two movies starting at the exact same time in different rooms. No input (parameter) is possible for this constraint because is more “permissive”, leaving the algorithm the option to decide how many minutes to put between movies.
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This constraint applies to all shows in a schedule.

No crowding for large rooms is a less permissive constraint.
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It has configuration options: the auditoriums to which it should apply (usually the 2-3 biggest rooms are included here); the time interval (the difference between the start times of the shows in that rooms); apply after (the hour when it should be applied).
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This constraint should not be applied to all auditoriums in a theater; this will cause long generation time because it's difficult for the algorithm to find possible combinations.
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In combination with the “no crowding” constraint, it should give you a schedule with a lot of shows starting at different hours.
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​Spread in starting times (when the same movie runs on two different auditoriums, the starting times should be at least X minutes apart)
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This refers to copies of the same movie (or more precisely, the titles with the same Group ID) “spread” in time. The time interval refers to the minimum minutes allowed to have between two copies of the same movie.
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