Yosef Karo

“ We have the custom to kindle an additional light, in order that if one uses its illumination, it would be the additional light, which was kindled last, and it should be placed at a small distance from the other obligatory lights. ”

“ Paragraph 2 — The kindling accomplishes the commandment; therefore if one extinguished it before its [minimum] time had passed, he is not bound to [rekindle] it. Even if he extinguished it on the Eve of Sabbath before accepting the Sabbath, when it is still daytime, he is not bound to [rekindle] it. ”

“ And even on the night of the Sabbath that is in the middle of the days Hanukkah it is permissible to kindle the Hanukkah light with the oils and wicks with which it is prohibited to kindle the Sabbath candles.
Rema: [this is] if one only puts in the light enough [oil] for the measure of its mitzvah. (Responsa of Shlomo ben Aderet Section 170) ...since it is prohibited to utilize the Hanukkah light whether on the Sabbath or on a weekday, even to check [the authenticity of] coins or to count them by its illumination; even a holy use is prohibited, such as studying [Torah] by its illumination. ”