Hi. The AG 400 Series is a Modulating Pilot SRV design. Actual Blowdown will depend on fluid and inlet piping configuration etc. Typically though, this design will return 3 to 4 % blowdown.
Note that some manufacturers claim 0 % blowdown.Here they will claim that since the valve is of modulating design, the valve will open and close according to the pressure rise and decay!. What you have to understand is that Pilot Operated SRV's are made up of 2 valves. The main valve and the pilot valve. All to often claims are made against the pilot valve only. The main valve governs the flow.
Per ISO, only the term Safety Valve is used regardless of application or design.