How to expand the sort range of rows in Excel?

Question

excel

There is a complex report file, to which there is no full access.
After reaching a certain number of rows, starting from row N + 1, selection and sorting by column stopped working correctly.
It is visually seen that the last line N, in contrast to the lines below (N + 1 and beyond), is highlighted in blue.
How to find where in the table the N threshold is indicated for the filters of selection and sorting by values ​​in columns?