Commonly, Asian keyboard layouts such as Japanese and Chinese use full-width alphanumeric characters to match the full-width han characters. These are different Unicode characters. When the author enters 2 as the Numeric answer, Möbius does not recognize the correct answer if the student writes full-width 2.
In order to properly allow for questions to be written in hanzi or kanji, without changing keyboard layout for Arabic numerals, Möbius would need to allow for the Unicode and/or GB 18030 full-width versions of the Arabic numerals, some punctuation, etc. Alternatively, it might be more appropriate to have a setting where you can force conversion to half-width.