Microwaving potatoes has a lot of variables to consider, so it is hard to give you a definite answer. The wattage of the microwave varies. Counter top microwaves are usually less powerful than the ones mounted above the oven or wall mounted. The size of the potatoes also makes a difference.  A 70 count, the size usually sold loose in a retail grocery store, averages 11-12 ounces. These typically take 5-6 minutes for the first potato and each additional potato adds another 3-4 minutes. I’ve had the best success wrapping each potato in a paper towel to absorb some of the steam that escapes and poking the potatoes with a fork in several places to also help the moisture escape from the interior of the potato. The internal temp of a fully baked potato is a minimum of 185° to 210° F, which can be checked after baking with a meat thermometer placed in the middle of the thickest part of the potato.