prussdrv.h constant definition

I would like to ask about constants like PRU_EVTOUT_0. In prussdrv.h PRU_EVTOUT_0 defined as:

#define PRU_EVTOUT_0 0
But in all examples that deal with PRU PRU_EVTOUT_0 constant is defined as:

#define PRU_EVTOUT_0 3 // the event number that is sent back
So why PRU_EVTOUT_0 definitions are not the same in header file and p-files?