Steps found in the ProxySG Administrator Guide here
Time quotas: Limit the amount of time that users can spend on the Internet or Internet resource during a specific period of time.
The time recorded in a quota is determined by the timing of client requests. If any client requests are initiated within a 60- second time period, the time in the user's quota increases by one minute. If any client requests are initiated after a 60-second time period has elapsed, a new 60-second time period begins and the time in the quota is increased by another minute. This continues until the time quota is reached.
Note: To apply time quotas to HTTPS requests, SSL interception policy must be enabled on the appliance.
Note: Before installing quota policy, the quota library in the CLI must be enabled. Issue the following command:
Restricting a user's access to YouTube videos to 30 minutes a day within a specified period of time. Create the following policy: