I think the point here, Alex, is that all values of the independent variables that are sufficiently close to but not equal to given prescribed numbers holds as long as you have a finite number of 9s trailing after your 2. You can add 9s arbitrarily and you will get closer and closer to the limit of 3 as long as you have a finite number of 9s. Once you reach an infinite number of 9s (not possible in the real world, but what the notation 2.99999... means) you are outside the realm of the defintion you quoted. You are no longer approaching the limit, you have reached it.