Driving liquid, which comes in main flow direction out of the nozzle installed in the water-jet pump, is accelerated by the diameter reduction of the nozzle. This acceleration causes low pressure at the suction spigot end sucking liquids or gaseous media.
The suction volume is a function of the driving liquid pressure and the nozzle bore.

Jet pump is used for:

pumping
mixing
vacuum production

Driving fluid flow is depending on nozzle hole diameter.
Vacuumed fluid flow is depending on:

driving fluid flow
jet pump outlet pressure (counter pressure)
Vacuumed liquide deansity
heigh of liquide charge or vacuum

Vacuum production is depending on driving fluid pressure/flow

Jet pump choice must be done from diagram including different uppers data.
Jet pump is delivered undrilled nozzle. setting must be done successive drilling untill good diameter.
A set of diagram pressure/hole/flow, for water/water or air /water, is at your disposal.