What causes the different size in grid cells?

Hey guys I have two sites, and they have the same design. Long story short I have to redesign it. When I was working on the redesign I noticed that one of them have tighter grids than the other. Both design have exact same format settings. Clearly, there are some other factors causing this difference.

Both sites have the same window size, there are no zooming applied. One grid is tighter with white side padding. Both sections share the same "Format" setting of 22 row counts and 11 grid gap. I am also not using any custom templates, I build with blank sections, so how do I achieve the tighter grid structure?

You can change the grid with the GAP property in the section settings.

thanks