First, if someone tells you they don’t get what you meant, you didn’t spell it out quite clearly to them, so to tell them that you did misses the entire point of communicating which is to communicate. You can be a jerk and come back with a snappy little answer or you can just rephrase, in case you weren’t clear. I know it must be difficult to imagine that you might not have been clear to someone, but it happens.
Second, you said they were undercounted, so how do we know anything about their numbers? And I’m done taking to you since you apparently think whatever you say is correct and above discussion. What’s the point of having one?
Second, you said they were undercounted, so how do we know anything about their numbers?
One would expect that a number of illegals would do their best to avoid being counted, so the total number is probably low - but I also doubt that upwards of 70% of them would be able to completely escape notice.
So while I can definitely believe that the census figures are off by several million, I don't think they are off by as much as 15 - 20 million.