Adjust your code block from Step 2 to include the data-suffix attribute as demonstrated below.
<div data-wm-plugin="pricing-table"
data-source="/toggle"
data-suffix="true"
></div>
To adjust the styling, add the below code to your Custom CSS area and adjust the values to your liking.
div[data-wm-plugin="pricing-table"] {
--suffix-content: 'per month';
--suffix-two-content: 'per annum';
--suffix-font-size: 12px;
--suffix-spacing: 5px;
}