Please double check that your free format's variables are the correct type for the HTML you are using. For example, if a variable is set to radio but the HTML is for a dropdown, you'll get that error.
sys_DataSource records where the data came from. Test survey is 4, live survey is 1, data generator is 6, etc.
sys_RespStatus records the current state of the respondent in the survey. An incomplete data record is 2, a disqualified respondent is 4, and a completed respondent is 6.
sys_DispositionCode is a custom value you can define in terminate questions. Useful for quickly determining which terminate question a respondent ended on.
sys_CAPIDeviceID records which CAPI device the data was collected on. Irrelevant if you are not doing offline surveying.