In case of import of a hierarchy, the complete file is loaded and then the lines will be ordered by the hierarchy criterion. Then the import will be executed. This results in 2 problems:
1.) The line counter is already on maximum when importing the first line, because the whole file has already been loaded. In case of an error, the last line number will be written with the error.
2.) Because the lines are ordered, the original line number gets lost. So this problem cannot be solved that easily. The DataImporter has to be extended, in order to keep the original line numbers and write them to the log along with the error message.
Enhancement request number 27147 has been submitted to Development for consideration in a future release of the product