To reset the connection counters back to zero:
(Under the Config Owner)
css#(config-owner) zero
or
(Under the Content)
css#(config-owner-content) zero
The command used on the CSS to clear all statistics is the "clear statistics" command. This command would basically reset all the Ethernet errors, MIB-II, and RMON statistics on a CSS Ethernet interface to zero. If it is not specific to a particular interface it would clear it on all interfaces.
To clear the counter of hits per owner or per rule, you can use the command "zero all" at the config owner prompt, or enter to the specific rule and use the same command.