There's a lot of green dots on that map so delays of less than 15 minutes.
Flow control in the US and Canada is for the most part dynamic. Certain airports and routes are flowed and ATC requests a time on taxy and for the most part delays are minimal even going to the bust airports.
When an airport experiences a reduction in capacity for weather or construction, then Ground Delay Programs are implemented with a target arrival rate. This is more like how Europe operates. Times are known in advance and delays can be late notice and extensive, especially for late filers or GA that operate outside a normal schedule.
The Ground Stop happens when a temporary reduction in capacity has led to backlogs of airborne inventory and further traffic from close by locations is stopped to facilitate a clearing of the backlog.
Our tolerances are +/-3 except destination ORD which is -3/0.