The signal current corresponds to flow rate of the instrument.

Need to know the flow with corresponding mA output?
Flow = ( (mA − 4 ) / 16) × ( Vmax − Vmin ) + Vmin

Need to know the output mA flow with corresponding flow?
mA=(16*(Flow-Vmin)+4*(Vmax-Vmin))/(Vmax-Vmin)

Example MVM-005-QA
Flowrate 0 .. 5 l.min

What is the flowrate with 12mA?
((12mA - 4)/16)*(5-0)+0= 2.5 l/min

What is the flowrate with 2.5 l/min
(16*(2.5-0)+4*(5-0))/(5-0)= 12mA

The QA versions has a flow range and max flow rate.
The MVM-005-QA has a flow range of 0..5 l/min but a max flow rate of 6 l/min.
The QA series has a current output cap of 21.5mA.
Max current output flow is 5.47 l/min, if you need the 6 l/min as output please use pulse/frequency signal.