I just found the solution in this forum. thanks
Create a file for the following path: module_name/static/src/css/pos.cssunder the pos.css file -
pos-product-line {
font-size: 14px;
}
You can also use t-style tag in your template to add the css
Copy codet-name="OrderReceipt" t-inherit="point_of_sale.OrderReceipt" t-inherit-mode="extension" owl="1">
t-style="{'font-size':'14px'}">
expr="//div[@class='pos-product-line']" position="attributes">
name="style" />
It's important to note that this will change the font size of all product lines in the receipt, if you want to target a specific product line you need to use a more specific CSS selector
Hope it helps