To turn off tube You need to send 64 bit of zeros via SPI interface.
int nZero=0;
SPI.transfer(nZero); //16bits
SPI.transfer(nZero); //+16bits - 32bits
SPI.transfer(nZero); //+16bits - 48bits
SPI.transfer(nZero); //+16bits - 64bits
I think the best solution is to change the function ‘void doIndication()’ at ‘doIndication314_HW2.x.ino’ file.