is extreme data considered as normal data

Some sources say that extreme data is that which is on the boundaries of the acceptable range. Other soures say that extreme data are out of normal boundaries.

extreme data are the values at the upper or lower limits of the expectation that are accepted. For example,
"A system has validation to ensure that only integers between 1 and 10 are entered as an input."
The extreme test data for this would be: 1,10 because they are at the boundaries of the accepted range.

so to answer the question, no, extreme data is not considered as normal data because normal data is within the range of data, only being 2-9.