Low fuel pressure.
 

Have a 2008 f350 bucket truck 5.4l. 175k. CEL came on. Scanned it and came back with a low fuel pressure code. Pulled some readings and I have two line items named "FUEL RAIL PRESSURE" and FUEL RAIL PRESSURE-DESIRED"
Can anyone tell me the difference or why

I'm using the enginuity scan tool. I've attached a copy of some fuel pressure readings. Can anyone tell me if these reasons are normal or what the proper range should be? That "desired" reading has guy me confused. It's obviously wrong but what would cause that reading? I'm hoping sensor. Looking forward to hearing from somebody.

Thanks
https://cimg0.ibsrv.net/gimg/www.for...559988fe6c.jpg