Unread post count not come properly

I am use discourse api for discussion forum.
I got one issue .
When i reply to topic that time not come unread post count in other user account at some of time .

I can’t understand what this means. Can you clarify?

I have two account one is ‘A’ and other is ‘B’.
Now i reply to topic from ‘A’ account and get api call for latest topic list from ‘B’ account that time not come 'unread count 1 ’ in api json .It happened some time not all time.

for example : Topic title ‘Hshajjs’ topic unread count some time come and sometime not come when reply topic from other account.