the dimensions required to run on HTML and your phone would be two separate processes.
Typically, you wouldn't need to change the code's dimensions, except for the viewport dimensions that the site sets to view the project. That is, when you decide which version to opt for. From what I learned is that if you specify the dimensions for a cellular device, it can also run on a PC device but not vice versa...
Hope this helps. Feel free to comment or correct me if I'm wrong.