§ 363. Supplemental appropriations. The board of supervisors, during a fiscal year, by resolution, may make additional appropriations or increase existing appropriations, the funds therefor to be provided from any unencumbered balances in appropriations pursuant to section three hundred sixty-four of this article, the contingent funds pursuant to section three hundred sixty-five of this article, or unanticipated revenues and unappropriated unreserved fund balance pursuant to section three hundred sixty-six of this article, or pursuant to the local finance law.