Use the <event-count> Web Component in HTML code:

<style>
    --event-count-event-background: red;
    --event-count-event-color: white;
    --event-count-count-background: teal;
    --event-count-count-font: 2.5rem Arial;
    --event-count-count-color: gold;
    --event-count-text-font: .7rem Arial;
</style>

Style shadowDOM with ::part(...)

<style>
    event-count::part(event) {
        background: gold;
        color: blue;
    }
    event-count::part(count) {
        text-shadow: 2px 2px 2px black;
    }
    event-count::part(year) {
        color: beige;
    }
</style>
            

styled with ::part