Question - Please help

I started to look at renko bars.

My first impression was WOW.

there is defnitely value in it but also doing a cross check there are things I dont get:

Example 1: in jun09 the top and the bottom of the Renko candle do match the exact top and bottom at the time.

Example 2: just recently the bottom traded was 2040 but the renko candle shows 2066.

I now understand why it looks so good by removing extremes but how does it work really?

QUestions:
1 what is happening?
2 how does it work?

so i can make sense of it.