Source Details?

Firstly, I’m a satisfied user and have made several DVDs successfully with this neat program. The following is more a matter of satisfying my curiosity.

Having made my last test DVD (which plays fine), I looked at the information about its first title (‘segment’) and saw this:

Source Details
-Input file type:
-Estimated Frame rate: 0.00
-Auto target: Ntsc 29.97 Fps, by Frame duplication
-Duration: 00:00:54.280
-Aspect ratio: 0.0000 (0:1)

Q1. Why no file type? (This is an AVI. Same empty entry for all titles.)

Q2. Why is NTSC specified, when I have PAL set permanently? (Note: final DVD looks fine.)

Q3. What does that Aspect ratio entry mean? (I am set to 4:3)

Terry, West Sussex, UK