The volume data is largely a ‘delta Cumulative’ indicator with the colours reversed to spell out the fact that ‘Dumb Money’ buys on red candles and sells on green candles (cos who doesn’t place limit orders and wait for retraces?)
The SL levels are simply gaps in the volume profile.
NT = recent gaps on wings
MT = = session gaps that have been in play some time, and/or acted as pivotal levels a few times
LT = Longer term session gaps.
The SL levels are NOT accurate order flow information. But simply an algo guessing where they are likely to be.
There will be a bit more to it than that no doubt, but that is the overall gist of it, and explains why so many DM SL levels appear on absolute textbook support and resistance level, where every retail trader and his dog was taught to enter trades on…NOT place their damn SL on.