Hello,
I get it, you are in Add to cart legacy mode, and sometimes there is some <br> that can leads in some specific configuration to this, but you can use some css in your front_end css file, like this :
span.hikashop_product_stock_count br {
display: none;
}
I give you the precise
Css because that correct some of our development choice, usually we don't provide Css order, especially for custom your HikaShop.
Note : Have a look on
this tutorial
to reach and modify your
front_end Css.
Hope this will help you to fix this.
Regards