Unfortunately embedded content is hit or miss. Embedded content generally should take care of setting up its own font, size, etc. Most embed code does, it appears it might not be the case here. But again I can’t really help without more details about the problem. Never heard of that particular button set.
MIndbody Branded Web Tools allows integration of MINDBODY Online features into a website, so the user is not taken from the site when looking at class schedules, signing in or buying services.
It once used to be called Healcode, until Mindbody Inc. brought them out.