The Equalizer's job is to balance the charger's load, so that overall consumption doesn't exceed the main fuse or tariff limit. When the Equalizer detects a load increase in the building, it will quickly decrease the available power allocated to the charger. When the load in the building decreases, the Equalizer will wait a minimum of 10 minutes before allocating more power to the charger. It may take longer if there's a lot of electrical activity happening inside the building, for example the immersion heater turning on and off.
The waiting period is there to be absolutely sure that power is available. Some cars behave in unexpected ways following rapid increasing and decreasing in power - that's why reduction happens quickly, while the increase is slow.
Higher ramp-up times are more frequent in buildings where the main fuse has a lower value, because the 10-minute timer may reset because of load spikes.