All to do with size of cable and how the cable is run. I have seen many times where the sizes of MCB on a consumer unit are same or even bigger than the MCB supplying it where someone has bought one really populated.
This is very common with caravans where total supply is 16A but consumer unit in caravan has 16A MCB for sockets.
So what size cable in mm² and what type of cable SWA or Twin&Earth etc. And how is it run? Underground or through wall with insulation in wall.
This is not really a question for an on line forum especially one which has no pictures it really needs someone to physical inspect to answer this.