The guiding principle should be “little and often”, e.g. three minutes, four or five times a week (spaced practice is more effective than blocked practice).
You can see how much time a tutee has been spending playing in games each day from your tutor dashboard:
Go to "Manage Users" in the main menu.
Select the name of the tutee you'd like to see statistics for.
Click the "Goal" tab.
Days coloured green in the calendar represent the days the tutee met or exceeded the daily number of minutes set as the goal. Orange marks the days when they played some games, however did not meet the daily goal. On days coloured red, the tutee did not complete any games.
To change the daily goal, edit the number of minutes that you require the tutee to play per day. You will see the colours change accordingly in the calendar below.
Press the "Save" button to set the daily goal for next time.
Please note that only time playing in Story or Challenge games counts towards the time played. Time spent in any of the other areas of NumBots (such as the Custom Shack) will not count towards their daily total. Therefore tutees' time played will be less than their total screen time.
Also, tutees must complete a game in order for it to count towards their daily time played. Games are only saved once they have finished it, so if the tutee exits a game halfway through, we will not save the game, therefore the time they spent playing that game will not be added to their daily total.