Tar Permissions

I am creating a tar and bzip file using SharpZipLib on Windows and then extracting on linux using tar.

The permissions seem to be incorrect by default I was getting sticky bits and write only files.

I have attempted to set the permissions manually but they still seem incorrect for example.

TarEntry Entry = TarEntry.CreateEntryFromFile(Path.Combine(Name, File.Name));

Entry.TarHeader.Mode = 0x0640;

Archive.WriteEntry(Entry, false);

Still produces incorrect permissions.

What is the value that Mode needs to be set to for 750 and 640 permissions?

Is it decimal, octal?

Thank you for the help.