core-bundle/src/Resources/contao/models/FormModel.php
public function getMaxUploadFileSize()
	{
		$objResult = Database::getInstance()->prepare("SELECT MAX(maxlength) AS maxlength FROM tl_form_field WHERE pid=? AND invisible='' AND type='upload' AND maxlength>0")
											 ->execute($this->id);

		if ($objResult->numRows > 0 && $objResult->maxlength > 0)
		{
			return $objResult->maxlength;
		}
		else
		{
			return Config::get('maxFileSize');
		}
	}
public function getMaxUploadFileSize()
	{
		$objResult = Database::getInstance()->prepare("SELECT MAX(maxlength) AS maxlength FROM tl_form_field WHERE pid=? AND invisible='' AND type='upload' AND maxlength>0")
											 ->execute($this->id);

		if ($objResult->numRows > 0 && $objResult->maxlength > 0)
		{
			return $objResult->maxlength;
		}
		else
		{
			return Config::get('maxFileSize');
		}
	}
Get the maximum file size that is allowed for file uploads

@return integer The maximum file size in bytes