Custom styles – but one digit jumps

The site is in development locally so I cannot post a link but here’s a video:
https://youtu.be/geXi8PhlG2Y

I am using a shortcode:
[tminus t="21-05-2019 9:30:00" omitweeks="true" style="carbonite-responsive" id="ftgsummit"/]

I have imported the carbonite-responsive CSS into my style.css and disabled the loading of the plugin’s CSS file.

Can you tell me why the 10s digit moves every second? And how can I stop it?

.carbonite-responsive-dash {
	display: inline-block;
	vertical-align: top;
	margin-right: 4em;
	position: relative;
	color: #FFF;
	text-align: center;
	white-space: nowrap;
}

.carbonite-responsive-digit {
	font-size: 5em;
	font-weight: 700;
	display: inline-block;
	position: relative;
	margin-top: 4px;
	margin-left: 5px;
	margin-right: 5px;
	background-color: #000;
	padding-left: 0.2em;
	padding-right: 0.2em;
	border-radius: 0.1em;
}

.carbonite-responsive-tripdash .carbonite-responsive-digit { margin-right: 0 !important; }

.carbonite-responsive-dash_title {
	display: block;
	position: absolute;
	width: 100%;
	color: #000;
	font-weight: 700;
	text-align: center;
	margin: 0;
	top: 9em;
	white-space: nowrap;
	overflow: hidden;
	text-transform: uppercase;
}