Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/Statistical.php
public static function SMALL(...$args)
    {
        $aArgs = Functions::flattenArray($args);

        // Calculate
        $entry = array_pop($aArgs);

        if ((is_numeric($entry)) && (!is_string($entry))) {
            $mArgs = [];
            foreach ($aArgs as $arg) {
                // Is it a numeric value?
                if ((is_numeric($arg)) && (!is_string($arg))) {
                    $mArgs[] = $arg;
                }
            }
            $count = self::COUNT($mArgs);
            $entry = floor(--$entry);
            if (($entry < 0) || ($entry >= $count) || ($count == 0)) {
                return Functions::NAN();
            }
            sort($mArgs);

            return $mArgs[$entry];
        }

        return Functions::VALUE();
    }
public static function SMALL(...$args)
    {
        $aArgs = Functions::flattenArray($args);

        // Calculate
        $entry = array_pop($aArgs);

        if ((is_numeric($entry)) && (!is_string($entry))) {
            $mArgs = [];
            foreach ($aArgs as $arg) {
                // Is it a numeric value?
                if ((is_numeric($arg)) && (!is_string($arg))) {
                    $mArgs[] = $arg;
                }
            }
            $count = self::COUNT($mArgs);
            $entry = floor(--$entry);
            if (($entry < 0) || ($entry >= $count) || ($count == 0)) {
                return Functions::NAN();
            }
            sort($mArgs);

            return $mArgs[$entry];
        }

        return Functions::VALUE();
    }
SMALL.

Returns the nth smallest value in a data set. You can use this function to
select a value based on its relative standing.

Excel Function:
SMALL(value1[,value2[, ...]],entry)

@category Statistical Functions

@param mixed $args Data values
@param int $entry Position (ordered from the smallest) in the array or range of data to return

@return float