Goodness knows. Difficult though it is to understand/believe, FWIW I read it as meaning that he would probably know 'what goes where' in the CU if he knew 'which cable was which' of the three that he has cut - which he appears not to know! Further clarification is clearly needed.So is this an accurate summary? The OP has a 2way CU, with an incomer, a 5A fuse and a 15A fuse, and he has a garage with a cable coming from the house CU and new cables in the garage which he put in and are connected to a light and a socket, and he doesn't know what goes where in the 2-way CU?
Kind Regards, John