If the phone turns on normally, you missed the timing. Remove the battery again and try holding the buttons before you press Power.
If you changed the default privacy password and cannot remember it, you may need to use professional flashing tools or visit an authorized TECNO service center for a technical reset. How To Hard Reset TECNO T528
Use this method if you can still access the phone's menu. It will return the device to its original factory state. If the phone turns on normally, you missed the timing