@Chris, I took the info about the combat from the "Polish Wings 15, Supermarine Spitfire IX 1944-1946" by Wojtek Matusiak (2012, Wydawnictwo Stratus). It is also repeated in other online sources (sometimes without the hour), but the date, outcome, pilot name and his plane serial number is everywhere the same.
Polish Wings also claims that it was a first victory achieved of a 308th pilot flying IX.