Why choosing DEFAULT_REPLY_DELAY_TIME: 7000us?. Can/how i change it?

[TCT2001]

I am using DW1000Ranging_ANCHOR and DW1000Ranging_TAG in examples folder, my result (range) seems good (+- 20cm).

But when i decrease DEFAULT_REPLY_DELAY_TIME, the range increases quite a lot (+50 -> +2m compare to real range), so i try increasing DEFAULT_REPLY_DELAY_TIME, the range, however decreases significantly (-50 -> -2m compare to real range).

DEFAULT_REPLY_DELAY_TIME is inversely proportional to range, isn't it? Someone can explain this ? Thank you all !