Correcting Left Margin Using CSS?

Darter02

My galleries are both collage portrait & landscape. I've used CSS to round the corners, and then had to add CSS to modify the right margin in order to eliminate the squared corners that erroneously appeared there.

.sm-tiles-row-organic .sm-tiles-list {
  overflow: visible;
  margin: 0 0 0 -18px;
}

My left margin is now a lot narrow than the right. Does anyone know what is the correct CSS to offset the right margin the same amount of pixels?

Darter02

I figured what I needed to do. I found that adjusting the margin for the right evened things out.