The April 16, 2015, White House announcement of Szubin’s intended nomination includes a biographical paragraph. It states that he had been OFAC director since 2006 and, concurrently, “serves as the Acting Under Secretary for Terrorism and Financial Crimes at Treasury, a position to which he was designated in February 2015.”
That sentence is the White House’s. This site does not invent an earlier or later designation date. Congress.gov later treats the under-secretary nomination as PN371. Acting service is not Senate confirmation. The full Senate never confirmed him.