High danger chances are breakaways, but also rebound shots.
Throw it on the net and crash is how you generate high danger chances if the D-men don't clear the crease.
"As originally defined by War On Ice, 'Scoring Chances' indicate shots attempts that are taken from areas of the ice where goals are more likely to be scored. Attempts made from the attacking team's neutral or defensive zones are excluded.
Inside the zone, a shot is assigned a value of 1,2 or 3, depending on where it was from.
A rebound shot (defined as any attempt made within 3 seconds of another blocked, missed or saved attempt without a stoppage in play in between)
adds a point to this value. A blocked shot decreases the value by 1.
'Scoring Chances' are any shot attempts with a final value of 2 or higher. 'High-Danger Scoring Chances' are any shot attempt with a final value of 3 or higher."
Advanced Hockey Statistics | Hockey-Reference.com