lol that's what I said You don't comprehend very well, you said they provide a boost lol, they don't, each breaker has the same voltage going in, and each fuse breaker determines how hot the wire can go when appliance are drawing current, which is also a safety measure to prevent wires overheating in your house, and melting and catching fire, typically if you run a appliance that draws high wattage and amps typically higher than the limit of the fuse, the fuse will overheat and trip, because of the higher current being pulled through the fuse.
Basically however much current you draw from mains the internal wiring and fuses always heat up to a certain temperature, so the fuses prevent your wires from overheating, in case you plug a higher powered device on a 13 amp circuit breaker outlet with lower spec internal wiring, instead of a 30 Amp circuit.