Timer is not accurate when the time set below 1ms

when time set below 1ms , time is not accurate
timer set actual ouput
1000ms 1080ms
0.9ms 1014ms
0.8ms 0.84ms
0.5ms 0.7ms
0.1ms 0.2ms

This My test script . It is a PWN Wave.
#include
#include "variant.h"
int Pump1=11;
int Pump1_High_Time=100;
int Pump1_Low_Time=100;

void ontime_pump_high(){
digitalWrite(Pump1, HIGH);
Timer4.stop();
Timer4.attachInterrupt(ontime_pump_low);
Timer4.start(Pump1_High_Time);
}

void ontime_pump_low(){
digitalWrite(Pump1, LOW);
Timer4.stop();
Timer4.attachInterrupt(ontime_pump_high);
Timer4.start(Pump1_Low_Time);


}

void setup() {
// put your setup code here, to run once:
pinMode(Pump1, OUTPUT);
digitalWrite(Pump1, LOW);
Timer4.attachInterrupt(ontime_pump_high);
Timer4.start(10*1000) ;
}

void loop() {
// put your main code here, to run repeatedly:

}

Start by inspecting the DueTimer.h API and the Timer4 start/attachInterrupt usage shown in the report, including the relationship between the requested values and the observed outputs. Reproduce the timing measurements for values below 1ms and for 1000ms; done means the timer behavior is accurate or its supported resolution and limitations are clearly established.

Written by the indexing model from the issue text.