'Normal' is used in a statistical sense - normal is not a point it is a range. If you like,consider the average (mean) of the trait that you are measuring, typically 'normal' is a range that falls around the average point.
Take height of 1000 people, the average may be 5'8", there of course will be a range it could be from 3' to 7', variation can be measured by a range of statistics, but for the example we with use standard deviation and say that the standard deviation is 6", hence given that the sample is roughly normally distributed, 95 % of the values are within two standard deviations, hence 95% of the heights are likely to be within 12" of the average height. Clearly in this sample those people that measured 3' and 7' foot are not 'normal' relative to the measure population trait.
Normal is not a measurement of value, it is merely a statement about variation around population mean of a measured trait – hence Aspies at <1% of the population are probably outside the normal distribution range for a measured population.