I need education on the Thermoquad "staged accelerator pump" , that gives an additional shot when the secondaries open

The pump shot plunger is spring loaded and moves a certain amount for the initial pump shot for the primaries. Then there is a time when the throttle arm continues to move without the pump shot linkage engaging the pump shot lever connected to moving the plunger. Depressing the throttle more moves the linkage up into the taller slot. The linkage is shoved to the top pushing the arm upwards some more for a second pump shot.