If what you are trying to do is display the field/value of an extra field named "RunningTime" then do this:
Code:
{section name=field loop=$extra_fields}
{if $extra_fields[field].active eq "Y" && $extra_fields[field].field eq "RunningTime"}
{$extra_fields[field].field}: {$extra_fields[field].field_value}
{/if}
{/section}