On average, your friends may have more friends than you do. It is not a trick of social media; it is a feature of how networks are sampled.
To appear on someone’s friend list, a person must be chosen by at least one other person. Highly connected people have more chances to appear on many lists, while someone with few connections appears less often. So when you look outward from a person to their friends, the sample is weighted toward people with larger networks.
In a network, this makes the average number of friends held by your friends tend to exceed your own number, a result called the friendship paradox. It describes an average, not every friendship: some people’s friends are less connected, and in a network where everyone has exactly the same number of connections, the effect disappears.