How to get the row count from block “products by category”?

I have a (woo commerce) post/page that uses shortcode

<!-- wp:woocommerce/product-category {"rows":30,"categories":(29)} /-->

Is there some way of getting the row count from the result (the fetched rows)?

I see it’s possible in raw PHP, somewhere, but I mean as a part of this “block call”.

I ask this because I use a code from stackexchange that gives the “count” of a category (products in that category), whilst the “block call” gives products from both the requested category-id and any child-categories.

I had a block showing three computers but the count was zero, because the “computer” category had no products – just the child categories.