Hi there @trandall0320!
The days display vertically when there isn’t enough horizontal space to comfortably display them horizontally. Usually that’s on mobile devices with smaller screens like phones, but it can also happen depending on your theme and how much width is available for displaying content in your theme.
You might check your theme for a full-width page option to make a bit more room.
If you need more help, can you send a link to the page where you’re embedding your booking form so we can take look and make some suggestions?