I had initially suggested this but then went and checked in the source and the largest unit in the format is hours. 52da4e40ea/src/util.cc (L518-L534)
52da4e40ea/src/util.cc (L518-L534)
Using .file kind and .downloading file operation kind will produce a more appropriate localizedAdditionalDescription. The fileTotalCount and fileCompletedCount aren't appropriate for this case, because there's only one file being downloaded.