If the Gmail uses the conversation view, Gmail does not display the right number of email messages in your account. It displays a wrong message count. Turning the conversation view off is needed to see the real number of individual messages in your Gmail account.
By default, Gmail groups a message and its replies in a conversation that’s listed as a single inbox entry. Conversation threads are the recommended way to manage your email; they provide a fast, efficient way to see multiple related messages in one view. However, if you prefer to list messages separately, you can turn the Conversation view off. You can switch back at any time.