The note in the documentation is wrong: the line number is correct when using the -x option, even if the first line is skipped.

Example with Python 2.7:
---
$ cat x.py 
print(1)
print(2)
x

$ python2 x.py 
1
2
Traceback (most recent call last):
  File "x.py", line 3, in <module>
    x
NameError: name 'x' is not defined

$ python2 -x x.py 
2
Traceback (most recent call last):
  File "x.py", line 3, in <module>
    x
NameError: name 'x' is not defined
---

Attached PR 4423 fixes Python 2.7 documentation.