From this link, you can access all the .NET versions most recent as well as previous ones in MSI and ZIP formats. (From similar links, you can access the Java and other Platforms versions)
The link you provided in the first post was like you are downloading entire family of Aspose.Cells.
Web Team then zip the entire family of Aspose.Cells (i.e. all Platform versions) and provide you a merged zip file. (This is not a good choice besides it is also not working as you said, so we will report it to Web team asap.)
We are sorry for the inconvenience and request you to download (individual) Aspose.Cells as per your Platform instead of (entire) Aspose.Cells Family.
We are pleased to inform you that our web team has fixed the issue now. You may download Aspose.Cells Product Family here which gives correct size of the archive now: