[DVD-o-matic] external Audio / pad with silence

Hello! Yesterday I made 3 versions of a DCP with a little video, and because its mono, I wanted to try how it would sound like when the audio is C, LR and LCR. So I exported a mono uncompressed wav file from Adobe Premiere. I tried to listen to the file with VLC Player and looked at the codec (PCM L16 SE) and thought everything was fine. But in the cinema, the sound was only LR, no matter what, and was pitched down like crazy. Didn?t sound good at all :) What did i do wrong? Is there a problem that the video file has audio too, and i just choosed external audio, is the video file not allowed to have audio? And my secound question, I?m not sure what "pad with silence to X channels" does and what I do with it. It?s not written in the manual. Can I get a short explanation? Thanks and greetings from Vienna! Andi