The county is indicated by a code number under the "CO" column. You can find a list of number codes for California counties at
http://helpdesk.rootsweb.com/FAQ/CA_Codes_Table.htmlIn the sample image you linked, the underlined names George Kozlowski and Tommie Wells show that the county code for their record is 19, which is Los Angeles County. Note there is a separate code for the CITY of Los Angeles (which is also true for San Francisco, San Diego, and Alameda cities.)