When using exclude rules, it is important to understand what you are telling the system to exclude on.
E.g. I have a Customer Trait called Reward Scheme. This reward scheme has bands Bronze, Silver, Gold. I am planning to introduce a Platinum level in the future, so I want an audience that excludes Bronze and Silver customers.
To make sure you exclude the customers you must use 2 different Exclude criteria as below:
Exclude Customer when Reward Scheme is Bronze
Exclude Customer when Reward Scheme is Silver
Note that if you try to Exclude where Customer Reward Scheme is Bronze and when Reward Scheme is Silver, this makes no sense to the computer as Rewards Scheme can't be both Bronze and Silver at the same time.