Similar (but different, please read on) questions have been asked dozens of times, so I'll try to be concise about this one.
The wording on protected questions "posting an answer now requires 10 reputation on this site" is incorrect. I have 60 reputation on the Physics SE site, but when I tried to post an answer on this question I was greeted with the protected message warning:
Thank you for your interest in this question. Because it has attracted low-quality answers, posting an answer now requires 10 reputation on this site.
This is buggy documentation. I do have more than 10 reputation. If the origin of those points affects whether or not they're counted this should be clarified in the message (in this case the association bonus is not included, so the word earned might be appropriate, although still subjective). Previous gripes with this message were posted in these questions:
Can we get a better wording for protected questions?
Improve "Protected Question" message with regard to rep gained through Association Bonus
There are probably more. In these posts, the questioners were asking to improve the wording to clarify that the association bonus is not included. Since then, the word earned has been removed, so now the wording is not just confusing (as pointed out in those questions), it's simply wrong.
A previous question with the same message was posted, but this question is not a duplicate because it requests to change the feature, I'm asking for it to be correctly documented:
I posted a physics meta question about this here:
Message incorrectly claims I need 10 reputation points to answer, when I already have 10 points
Unfortunately it was closed as duplicate, which I do not believe to be warranted. A commmenter suggested I post it on Meta SE.
