Meanwhile he was waiting for his train, he noticed 58132 PURI - ROU Passenger with BNDM WDM-3D #11165, standing at a short length PF (terminal type, having a dead end) adjacent to PF No 1. The train left SBP after some time.
My friend informed he that he observed water filling pipes beside the track for that PF. That means, the short PF is also separately used apart from the main 3 PFs in SBP. Although there is no marking (i.e. numbering) at that PF.