Odd Use of Watch Dog Timer

What I meant of Odd Use is the result not my expected but exactly what I needed. I experiment 7 segment LED display driven by 74HC595, I found the circuit and the code to build on, I previously built the DHT11 and 1602 LCD to test the temperature and humidity without problem, now I give it a try to display with 7 segment LED. I found a problem, I cannot run the getData() and displayData() simultaneously in the loop() function, the left three digits kept on flickering, though I still can guess it.”

Link