Solved!
Changing two lines in "func_display.php" and replacing "(int)" and "(int) round()" on lines 285 and 326, both to "number_format" with 2 decimals. And now percentages are more precise!
Original lines (285 and 326):
$howmuch_1 = ( int ) ( $value / $sum_total * 100 );
echo (int) round ($howmuch_3)."%";
Replaced lines (285 and 326):
$howmuch_1 = number_format (( $value / $sum_total * 100 ),2);
echo number_format($howmuch_3, 2)."%";
Hope this changes can help to someone