data: a string (values between 0 and 255) that contains uint8 numbers
startUint8Index: the zero-based index from which on data should be unpacked (from data[startUint8Index]). Can be omitted in which case 0 is used.
uint8Count: the amount of uint8s that should be unpacked. Can be omitted in which case 0 is used (which indicates that the maximum of uint8s should be unpacked from the indicated startUint8Index).