Question about Social Media Management service. BUFFER

So I just registered to buffer(social media management service), they have the option to add 10 accounts under one platfrom in their free trail, but what I want to know is, I have like 7 pinterest accounts and I have different private proxies for all of them and if I use all those pinterest accounts on buffer, is there going to be a problem, since they don't really give you the option to use proxies.
so how does it work? Do they have their own proxies or is it something else?

Just put 4 to 5 to be safe, and i don't think that they have their own proxies, especially not for the free version...