Each property will autocomplete to the standard Android SDK values, or you can provide custom values, e.g. if you have additional platforms defined or want to use a custom resolution.
You can also do environment variable substitution for any of these properties, in the format: ${VARIABLE_NAME} or $VARIABLE_NAME.
For example, if you have configured a matrix build to include a "density" axis with values "120 160 240", you could enter ${density} for the "Screen density" property below and the appropriate substitution would be made when each individual build is executed.
Emulators are stored in the usual $HOME/.android/avd directory, named in the format: hudson_[locale]_[density]_[resolution]_[target].