Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/Statistical.php
public static function COUNT(...$args)
    {
        $returnValue = 0;

        // Loop through arguments
        $aArgs = Functions::flattenArrayIndexed($args);
        foreach ($aArgs as $k => $arg) {
            if ((is_bool($arg)) &&
                ((!Functions::isCellValue($k)) || (Functions::getCompatibilityMode() == Functions::COMPATIBILITY_OPENOFFICE))) {
                $arg = (int) $arg;
            }
            // Is it a numeric value?
            if ((is_numeric($arg)) && (!is_string($arg))) {
                ++$returnValue;
            }
        }

        return $returnValue;
    }
public static function COUNT(...$args)
    {
        $returnValue = 0;

        // Loop through arguments
        $aArgs = Functions::flattenArrayIndexed($args);
        foreach ($aArgs as $k => $arg) {
            if ((is_bool($arg)) &&
                ((!Functions::isCellValue($k)) || (Functions::getCompatibilityMode() == Functions::COMPATIBILITY_OPENOFFICE))) {
                $arg = (int) $arg;
            }
            // Is it a numeric value?
            if ((is_numeric($arg)) && (!is_string($arg))) {
                ++$returnValue;
            }
        }

        return $returnValue;
    }
COUNT.

Counts the number of cells that contain numbers within the list of arguments

Excel Function:
COUNT(value1[,value2[, ...]])

@category Statistical Functions

@param mixed ...$args Data values

@return int