Bottom padding for GridStack container

[Artgit]

I was successfully able to add top padding to GridStack container by providing a following styles:

[class*=' grid-stack-instance'] {
       .grid-stack-item[data-gs-y="0"]{
         top: 10px;
     }
}

I also need to add the same padding to the bottom of GridStack container.

The following style unfortunately doesn't work:

[class*=' grid-stack-instance'] { .grid-stack-item:last-child{ bottom: 10px; } }

How it can be implemented ?