Arduino mkr gsm 1400 sleep mode

Hello ,
I trying to make project, where i need a low power consumption on my arduino mkr gsm 1400, i tried libraries like RtcZero, and arduionoLowPower.h, but the lowest values i received is 24mA, i tried to shutdown gsm module with gsm.shutdown(), but the difference is about 4mA.
Does anyone have any ideas how i can obtain like 12mA?
I can unsloder the green led, but it i will not win too much.

This is one of the codes i tried:

#include <GSM.h>
#include "ArduinoLowPower.h"

#define PINNUMBER "1234"

GSM gsm; // include a 'true' parameter for debug enabled

void setup()
{
pinMode(LED_BUILTIN, OUTPUT);

}

void loop()
{

// initialize serial communications
Serial.begin(9600);

// connection state
boolean notConnected = true;

// Start GSM shield
// If your SIM has PIN, pass it as a parameter of begin() in quotes
while(notConnected)
{
if(gsm.begin(PINNUMBER)==GSM_READY)
notConnected = false;
else
{
Serial.println("Not connected");
delay(1000);
}
}

Serial.println("GSM initialized");

digitalWrite(LED_BUILTIN, HIGH);
delay(5000);
digitalWrite(LED_BUILTIN, LOW);
delay(500);

gsm.shutdown();
Serial.println("GSM terminated");
LowPower.sleep(10000);
}