I just followed your instructions, downloaded RaspPi loader on Windows… ran w new 64GB high speed micro SD card… and opened in Windows after successful Ubuntu 20.04 LTS Desktop install to card (selected exactly as on screen option and OS rev…), and from windows only shows the card is 197 MB used of Total 252 MB SD ??? (what about the rest of the 64GB card !??.. it only formatted the size of the Ubuntu image ???)
That was not a Technical Support thread, so I have moved your comment.
Tutorial threads are ONLY for direct feedback on that tutorial: Fixing typos, updating images, etc.
For technical support questions like “Why does a .img file not fill the entire SD card” that are not Ubuntu-specific, please consult any generic technical support venue. Or ask your favorite Search Engine.
For Ubuntu-Specific technical support questions, please see https://community.ubuntu.com/t/finding-help/712.
This site is not for support questions, sorry.