In Touch Portal you can have different button grid sizes and settings per page.
With the grid settings number pickers you can set the amount of columns and rows. Try changing them from 4x2 to 5x3. All buttons will stay on their location within the grid but the grid expands so the buttons because a bit smaller.
With this option you can set the amount of space between the buttons. If you do not want any space between them, use 0.
When you select this option the buttons will expand to use the maximum available space within the grid. This means the background will expand and the icons will take the maximum amount of available space but it will keep aspect ratio.