a number counts as a prefix arg.
To kill a whole line, when point is not at the beginning, type \
-\\[beginning-of-line] \\[kill-line] \\[kill-line].
+\\[move-beginning-of-line] \\[kill-line] \\[kill-line].
If `kill-whole-line' is non-nil, then this command kills the whole line
including its terminating newline, when used at the beginning of a line
with no argument. As a consequence, you can always kill a whole line
-by typing \\[beginning-of-line] \\[kill-line].
+by typing \\[move-beginning-of-line] \\[kill-line].
If you want to append the killed line to the last killed text,
use \\[append-next-kill] before \\[kill-line].