it clearly says ,answer must be 6 characters long.

Look clearly at the error message you provided.
expected 'F22F7' to equal '0F22F7'

The expected answer is on the right side. The left side is the output of your function. So, the one that outputs the string with length 5 is your function. This is not kata issue.

I don't know what to say except that you're just wrong. Furthermore, you justify your position (twice) with "opinion". Correctness isn't a matter of opinion, though.

For example, in a rectangle 14x20, you find the square 14 (good), but then with the remaining 14x6 rectangle, you somehow conclude that the next square is 9. No idea where you get that number from.

This is not an issue. Please revisit your logic.