Yes. You can select the required device(s) and reports by following the procedure in the Settings > System > Customize Report link, to view only the required reports.
Bytes values shown in all reports are in MB. In case of low traffic value (i.e., less than 1 MB), it will be shown as 0 MB in Graphs & Tables. You can get full conversation data with exact byte value received by application in the Raw Search result report.
It is the average of data on that specific hour/day from the minute Firewall Analyzer is installed and running.