How announcement open rate statistics works?

Hi, when I send an announcement using Sendbird Announcements API
and check the dashboard after I sent to users, open rate is always 0%.

Here is the brief summary of our service.

Hopae API ->(calls) SendBird Announcment API → users in “Knock Messenger” (application name, you can check on AppStore or Google Playstore).

After we sent announcement and opened it in an application (when open it, it uses Sendbird SDK sendbird.GroupChannel.createDistinctChannelIfNotExist to show last message in chat room), it is not reflected to the open rate statistics.

What code should we use to raise open rate statistics of announcement in Sendbird?
Please let me which APIs should be used to raise open rate of Announcement.