Use box-sizing: border-box

macrovision.css

@@ -352,7 +352,7 @@ select {
 .options-row .options-field-numeric {
     flex: 0 1 50%;
     font-size: 150%;
-    width: calc(90% - 12px);
+    width: 90%;
     padding-left: 4px;
     padding-right: 4px;
 }

reset.css

@@ -22,6 +22,7 @@ time, mark, audio, video {
 	font-size: 100%;
 	font: inherit;
 	vertical-align: baseline;
+	box-sizing: border-box;
 }
 
 input, select {
@@ -31,6 +32,7 @@ input, select {
 	font-size: 100%;
 	font: inherit;
 	vertical-align: baseline;
+	box-sizing: border-box;
 }
 /* HTML5 display-role reset for older browsers */
 article, aside, details, figcaption, figure,