Keys Not Unique. Please fix before saving.
This message occurs most frequently when creating large option lists. This error means that the option list has two identical key values. To eliminate this error message you must change the key values so they are Unique.
To do this click on the advanced tab in the option list manager and change the duplicate KEY_VALUE to a unique values. In the example below, the KEY_VALUE "rent" is being used twice and must be altered to save correctly.