Is it legal to write on your USCF scoresheet?

So, I have heard that you are not allowed to write future-prospective moves on your scoresheet, you can't write moves ahead of time, and you can't just bring some text (a book, for example) to a USCF tournament you're playing in. At a tournament, I reached a tense position (probably not tense to others but it was to me, I think the two possible moves I had would've produced the same outcome), and I wrote possible lines that could occur in the game on the back of my scoresheet (and good news, I won and set my rating to 800 USCF!). Is that legal, just so I know for the future?

No, in big national tournaments, that is illegal. Don't do that next time!

"20C. Use of notes prohibited.
The use of notes made during the game as an aid to memory is forbidden, aside from the actual recording of the
moves, draw offers, and clock times, and the header information normally found on a scoresheet."

You can find the USCF Rules of Chess as a PDF File.

is this illegal for ecf too? my last opponent did this but i didnt care