open LOG,'logfile' or die "Can't open 'logfile': $!\n";
my $max = 0;
while (<LOG>) {
    $_ = substr( $_,27,6 ); # make sure the position and length are ok
    $max = $_ if $_ > $max; # if it's not numeric, it's 0 and never more than $max
}
print "max = $max\n";