needed to download data from nhgis website it is a cvs file that im trying to merge of the 2016 census of the poverty levels in california so that i can see the data from the file in the attribute table of my "study area" layer
The 'warning' could be corrected in the csv file prior to performing the join, if you can identify what field it is. The mismatch in records may indicate that more data is available than the number of locations in the destination table... that isn't an issue. The data in join fields are text-case sensitive if you have blank rows.
Hope you got it done.