You don't refer to a specific line number, but, generally, Column E is used for income from all sources while someone is a California resident, and income from California sources while someone is a nonresident.
For nonresidents specifically, it should reflect income derived from California sources.
If you're a full-year nonresident, then, for each line with a Column E on Schedule CA (540NR), you should follow the "California Nonresident Amounts" instructions related to each line in the Instructions for Schedule CA (540NR).
