How to resolve timevault encryption delay during macOS?

I'm trying to install macOS Catalina from macOS High Sierra. It's saying I need to wait 18 hours to encrypt my startup disk. Then, like, three hours later, instead of 15 hours it jumps to 8 hours. THEN, 3 more hours repeat 18 or something. What do I do?

[Re-Titled by Moderator]