Will a 63amp rcd handle four high mcb?

Hi, This is a poor installation of the consumer unit, and as this has been done without any understanding, get the rest of the home tested and inspected. The entire point of installing a dual RCD board is to split circuits for safety. So the lighting needs to be split as do the socket outlet circuits. Should you then have a fault on one circuit that trips the RCD, you only lose half of the lighting and sockets, this also means that you can easily detect that you have a problem. Just adding up the value of the MCB's then comparing to the RCD is not correct. However, even allowing for diversity this does look a little unbalanced, so get it changed. You can't just swap the cables going into the MCB's. Find a registered electrician, ask him to do an EICR and swap the circuits around whilst he is there.

You, or preferably an electrician need to spread the loading over the two RCD's. Just a matter of swopping, and knowing what you are doing. Or perhaps you could swap one of the 63 amp for an 80 amp.