Nadav,
Ahh that’s right- you are using the Social Marketplace / OneSocial, right?
They actually already are modifying that output– so I am going to have to send you to BuddyBoss to see if they can help with this. Without a lot of digging (their code is craziness.. seriously..) I do not know exactly what they have done to change the output of the upsells and linked products so that they appear on the left side of the page there. Normally, WooCommerce upsells/linked products use a hook for the bottom of the page, beneath the product details and tabs.
So– sorry but you will need to please ask BuddyBoss how you could work with their code to modify the output and only allow a particular number of upsells to show on the product page.