Hello, please follow the steps below:
1. In the 【System Settings】 menu, use the up/down arrow keys to navigate to 【Sleep Time】, then press the 【OK】 button to enter the 【sleep time】 menu.
2. The sleep time can be set between 1 and 240 minutes. Use the up/down arrow keys to increase or decrease the sleep time, then press the 【OK】 button to confirm. Holding the up or down arrow key for a few seconds will increase or decrease the sleep time by 10 minutes.