If you import the file with length restrictions and the cell or unit is divided to more segments (due to segmentation rules), the character limit for the whole cell or unit is checked against each of those segments separately, but not in total against all those segments together.
Available workaround (if any):
It needs to be checked manually, or the files need to be segmented in 1 cell/unit = 1 segment method.
Implement a character QA check against the total of all segments that make up one cell/unit.
Some users prefer to segment cells/units, especially when they consist of several sentences.