it's an statement that checks to see if the file size is -1:
if($WA_DFP_UploadStatus["WA_UploadResult1"]["fileSize"] == "-1")
if it is, it resets the file size to use the value that is already ion the database:
$WA_DFP_UploadStatus["WA_UploadResult1"]["fileSize"] = $row_WADADownload['DownloadFilesize'];