In a recent video, I was drawing rectangles. My input included @Anonymous,40, but in the recording it came out as 250,40. That could really mess someone up, especially a new user.
I had other input that used the @##,## input and all of them used a 2 instead of @.
It's been a while. My original post on this was Feb, 2017, before the 2018 versions were available, so, mostly likely, it was Civil 3D 2017..
I just tested it with Civil 3D 2018 and it still has the same behavior.
Here's a test video:
https://knowledge.autodesk.com/community/screencast/521b0333-d6db-46e8-ac4e-3cb2ac34e6a4
Well, the test video no longer shows the keyboard captures at all. It did when I initially viewed it. Odd.
Anyway, try it out.