You could leave out the day and create logs by month. See the help associated with the Options screen.
XML format is useful if you have Excel 2003. Prior versions of Excel do not import XML format. You should remember that the file format dictates that the end of the file be closed off with a closing structure field. So if the overall file starts with <ConnectionStatistics> then at the end of the file should be a <ConnectionStatistics> field. While the file is being written it will not have this statement and therefore would appear to be invalid if input to a program such as Excel. You can manually add in the closing statement (check the leading statement at the start of the file) or you can wait until a new XML file is created. FreeProxy will only place the ending statement if it knows about the starting a new file.
This is an internet standard and can be selected as log format in most web servers and proxies. A useful tool to analyse your logs in this format is Papercut. See http://www.papercut.biz. Papercut also has the ability to monitor internet usage and can apply charging rates usage.
User defined format is a format where you specify the exact format you want to see on each logged line. For example
2004-03-21, 15:33:12, 192.168.100.1, 80, ADESFred,www.yahoo.com,/
Only a few fields are shown for the example but you could use any of the allowed fields for the log type. Check the help for those fields that are allowed for each type of log. Not all fields are allowed for all logs. The useful thing about this format is that you can import this into all versions of Excel using the comma separated option.
xml file style log analyze analyse