I have a large new truck (over 6,000 lbs)  placed in service this year.  As long as I choose MACRS 5 year % Vehicles over 6000 lbs, No Limits from the "Method" drop down on screen 22 I get the full cost of the truck on form 4562 Part IV  (Summary)line 21 Listed property.  I have to enter the cost under Current Section 179 expense in order to have the cost show under Part I line 2.  Either way I get the write off in year one.  What is the technical difference/interplay between the screen fields?  

Also, unless I enter the amount under Current Section 179 expense the California 1=not eligible for state Section 179 {CA only} does not apply. 

Thank you