Welcome to WPSE.
You can try to filter it with:
add_filter( 'human_time_diff', 'wpse_hourly_human_time_diff', 10, 4 );
where the filter's callback is e.g.
/**
* Human time difference in hours only.
*
* @param string $since The difference in human readable text.
* @param int $diff The difference in seconds.
* @param int $from Unix timestamp from which the difference begins.
* @param int $to Unix timestamp to end the time difference.
*/
function wpse_hourly_human_time_diff( $since, $diff, $from, $to ){
return round( $diff / HOUR_IN_SECONDS, 1 );
}
but you will need to control where you want to apply this filter with:
remove_filter( 'human_time_diff', 'wpse_hourly_human_time_diff', 10 );
and further restrictions.
Hope you can adjust to your needs.