As can be seen from the first screenshot I uploaded above, I did open my Wokamon app before the day starts and hence why it is able to track my steps from 6.20am to 6.48am. The second screenshot above also shows that my Samsung Health app also started tracking my steps at around 6.20am.
However, the Wokamon app stopped tracking completely after 6.48am for reasons unknown and I did not realise that until I open the Wokamon app again at the end of my day at around 10pm. That is when it starts tracking my steps again.
Not sure if it is a bug in the app or a problem with my phone. :S This is the first time it happened - did not encounter this problem before.