The W should be an N in the heat pump model number. Probably just a transcription error. The air handler should be FE4ANB006***--unless he/she meant to write FV4BNF006***, and in this case this would not be an Infinity system.
All in all, you need your sales representative to give you the correct model numbers in writing before you sign anything. I'm willing to bet it's a transcription error.