Opening a microwave while it is running typically does not change the time or power level of its timer. Microwaves are designed to pause their operation when the door is opened as a safety feature. This is done to prevent any potential harm to the user by stopping the emission of microwaves.
When you open the microwave door, it will usually pause the cooking process and stop the countdown timer. The time and power level settings will generally remain the same when you close the door and resume the operation. However, it's worth noting that different microwave models may have slightly different functionalities, so it's always a good idea to consult the user manual for specific instructions and features related to your microwave model.