Make iframe of online booking tool smaller

When we insert the booking tool onto the website, it comes up way to large and is hard to use because of it. Would it be possible to have the option to reduce the size of font etc to fit in with the rest of the website a little better. To be able to assign a client to a resource eg special room which then can not be booked by another client at the same time (for example clients needing a specific treatment room)