To keep the decimals and add (2 decimal points if there are none), you need to change
$value = number_format($value);
$value = number_format($value , 2);
add_filter(‘acf/format_value/name=instrument_price’, ‘fix_number’, 20, 3);
function fix_number($value, $post_id, $field) {
$value = number_format($value , 2);
return $value;
}
see https://www.php.net/manual/en/function.number-format.php
