In a chat room, the default for view messages is the last 100. If a room has over 100 and a user leaves/refreshes the chat room, only the last 100 messages show. If they select the option to show the last 3 days worth, it will still only show the last 100.
The property file could be updated to include something like:
but it seems like the last 3 days option should show the last 3 days without having to set that option.