This shield just takes care of the wiring for you! Please note our Arduino library only supports 32-pixel tall matrices, so don’t try using a 64×64 matrix, it doesn’t work!” Source: Adafruit ...

MT8808 Functional Diagram from Datasheet The MT8808 is essentially an 8×8 matrix of controllable switches, which acts as the perfect tool to interface with the C64’s 8×8 keyboard matrix.