OK, looks like the 4th argument is the number of MAX72xx LED controllers daisy-chained together. You'd have to poke around to find the DataOut from the MAX72xx on the first module so you can connect it to the DataIn of the second module. If you do daisy-chain two modules, only digits 0,1,2,3 and 8,9,10,11 are likely to work since each 4-digit module has an 8-digit controller.