I want to display elements across all screen sizes

Question. I am currently using the following template(Messaging like Whatsapp Web Template | Bubble).

In Preview mode, the bottom margin of the message is very large as shown in the attached image(Red framed area)

. I would like to remove this margin and display this message screen in all screen sizes as a responsive design.

The current Layout settings for the group are as shown in the attached image. Since both width and height are set to “inf”, it is assumed that the message will be displayed on the entire display size, excluding the margin, but there is a waste of space at the bottom of the message.
I would like to know how to solve this problem.