Thumbnail dimensions

Hello, I’ve also written to support. In my theme the thumbnail of the course featured image does appear smaller that it should be.

The underlying html is this one

<div class=”tutor-price-box-thumbnail”>
<img width=”223″ height=”137″ src=”https://www.tuttosullapostaelettronica.it/blog/wp-content/uploads/2020/11/corso-posta-elettronica-featured-223×137.png” class=”attachment-post-thumbnail size-post-thumbnail” alt=”corso posta elettronica” loading=”lazy” /> </div>

but should be this one to make the thumb does appear correctly

<div class=”tutor-price-box-thumbnail”>
<img src="https://www.tuttosullapostaelettronica.it/blog/wp-content/uploads/2020/11/corso-posta-elettronica-featured.png” class=”attachment-post-thumbnail size-post-thumbnail” alt=”corso posta elettronica” loading=”lazy” /> </div>

Can you tell me why and how to fix it?

The page I need help with: [log in to see the link]