Hello Pui Lai
The command ip pim spt-threshold 0 is actually the default setting. So by default, the switch from the RPT to the SPT will happen almost immediately after the first data packet arrives at the last hop router. So this command is not needed unless you have changed it beforehand and you want to return to the default.
For more information about this particular command, take a look at this Cisco documentation:
I hope this has been helpful!
Laz