For steel design by AISC-360-05 why the 1.3*Dead load is used at autogenerate load combination? In the code the instruction is 1.2DL+LL+EL.
There is a knowledge base page set up by the developers with information related to the calculation of various elements and designs. I recommend checking the page then click on FAQ to see exactly the common answers to the problems found within the application.
FAQ page: https://wiki.csiamerica.com/display/etabs/Load+combination
On the left menu, you have links with various help guides.