Turn on all the lights in the model apartment that you want to come on when you open the entry door. Go to the breaker box, flip the first breaker to the off position, then walk through the model to see if any lights turned off. If any lights turned off tag that breaker and then flip it back to the on position. Next flip the second breaker to the off position, then walk through the model again to see if any of the lights turned off. If any lights turned off tag the breaker, if none of the lights turned off do not tag that breaker and flip it back to the on position. Go through all of the breakers this way. This will help you determine how many of your breakers actually carry your lights. Once you have gone through all the breakers count up all of the tagged breakers. If there are 6 or less tagged, a MM-6K is fine. If there are 7-10 breakers tagged you will need a MM-10K.