From the manual:
MangleAgents. Mangle user agent names according to the mangle level specified by num. Mangle levels are:
5 Browser name and major version.
4 Browser name, major and minor version.
3 Browser name, major version, minor version to two decimal places.
2 Browser name, major and minor versions and sub-version.
1 Browser name, version and machine type if possible.
0 All informaiton (left unchanged).
Mangle user agent names based on mangle level num. See the -M command line switch for mangle levels and their meaning. The default is 0, which doesn't mangle user agents at all.
If running with a -M command-line option, change to -M0. If using a config file, look for and change the MangleAgents line.