As defined in the survey documentation for 2013, TOTINCM (survey data element 304) is “ the sum of Local Government Revenue, State Government Revenue, Federal Government Revenue, and Other Operating Revenue (data elements #300 through #303).”
For complete information about the survey data points, please see the survey data documents available here.
We use the most recent data available but due to differing definitions of "fiscal year" across library systems and a lag time in the availability of the data, the information we have is generally from two to three years prior to the current calendar year. For example, in June 2016, the most recently available data is from 2013. That will be updated to the 2014 data when it becomes available. A list of the available data is here.