Hello,
By default, the traffic statistics function is disabled on ethernet sub-interfaces. Before checking statistics about sent or received packets on an ethernet sub-interface, run the statistic enable command in the ethernet sub-interface view to enable the traffic statistics function.
After configuring the command subinterface traffic-statistics enable globally, the statistics function is enabled on all subinterfaces created and it appears with statistic enable after display this command. This is how you will know that the traffic statistics are enabled.
If you want to disable the function, you can use undo subinterface traffic-statistics enable globally and on all subinterfaces, the command statistic enable will not show.