Your study time captures only the time you've actually spent studying in Voxy. You can check the following article to better understand how do we determine your Study Time.
The Performance Page monitors the time you spend practicing your course. Be aware that your Performance Page monitors only the time it takes you to answer questions in your activities and you can select the length of time you would like to check your study time.
Your calendar defaults to showing the current month up to today's date. To see your completed activities and hours for a different period, simply click the calendar icon and select a new date range.
The same applies to the number of completed activities: