Quota counter not consistent

[#1]

I am using a quota policy as below.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Quota async="false" continueOnError="false" enabled="true" name="CopperQuota" type="calendar">
    <DisplayName>CopperQuota</DisplayName>
    <Properties/>
    <Identifier ref="app.name"/>
    <Allow countRef="actualLimit"/>
    <StartTime>2017-2-23 12:00:00</StartTime>
    <Interval>5</Interval>
    <TimeUnit>minute</TimeUnit>
    <Distributed>true</Distributed>
    <Synchronous>true</Synchronous>
</Quota>

I have a requirement to send the current count in response. I am using js policy for this as below.

context.setVariable("CopperCount", parseInt(context.getVariable("ratelimit.CopperQuota.used.count"))); 

But I have observed that the count is inconsistent though I am triggering multiple requests within the 5 minute window. Is this an Apigee issue. Please confirm