@SAJain As suggested by @HemanginiS this string is occuring because it is being passed in the server call. What is being sent in the call is recorded and showed in the workspace project. You may want to extract the raw data by Data Feeds for the day when this string came and then you can check the condition when this value is fired.
Most likely you are passing "false:personal" as the actual value (string) in that dimension. If you can share more details like which variable/dimension it is and how you are capturing value into it then we can further look into it.